diff --git a/Tone/core/type/Frequency.test.ts b/Tone/core/type/Frequency.test.ts
new file mode 100644
index 00000000..b3593170
--- /dev/null
+++ b/Tone/core/type/Frequency.test.ts
@@ -0,0 +1,220 @@
+import { expect } from "chai";
+import teoria from "teoria";
+import { BasicTests } from "test/helper/Basic";
+import { Offline } from "test/helper/Offline";
+import { getContext } from "../Global";
+import { Frequency, FrequencyClass } from "./Frequency";
+import { Midi } from "./Midi";
+import { Ticks } from "./Ticks";
+import { Time } from "./Time";
+import { TransportTime } from "./TransportTime";
+
+describe("FrequencyClass", () => {
+
+	BasicTests(Frequency);
+
+	context("Constructor", () => {
+
+		it("can be made with or without 'new'", () => {
+			const f0 = Frequency();
+			expect(f0).to.be.instanceOf(FrequencyClass);
+			f0.dispose();
+			const f1 = new FrequencyClass(getContext());
+			expect(f1).to.be.instanceOf(FrequencyClass);
+			f1.dispose();
+		});
+
+		it("can pass in a number in the constructor", () => {
+			const frequency = Frequency(1);
+			expect(frequency).to.be.instanceOf(FrequencyClass);
+			frequency.dispose();
+		});
+
+		it("can pass in a string in the constructor", () => {
+			const frequency = Frequency("1");
+			expect(frequency).to.be.instanceOf(FrequencyClass);
+			frequency.dispose();
+		});
+
+		it("can pass in a value and a type", () => {
+			expect(Frequency(4, "n").valueOf()).to.equal(2);
+		});
+
+		it("with no arguments evaluates to 0", () => {
+			expect(Frequency().valueOf()).to.equal(0);
+		});
+
+		it("is evaluated in equations and comparisons using valueOf", () => {
+			// @ts-ignore
+			expect(Frequency(1) + 1).to.equal(2);
+			// @ts-ignore
+			expect(Frequency(1) + Frequency(1)).to.equal(2);
+			// @ts-ignore
+			expect(Frequency(1) > Frequency(0)).to.be.true;
+			// @ts-ignore
+			expect(+Frequency(1)).to.equal(1);
+		});
+
+		it("can convert from Time", () => {
+			expect(Frequency(Time(2)).valueOf()).to.equal(0.5);
+			expect(Frequency(Time("4n")).valueOf()).to.equal(2);
+			expect(Frequency(Time(4, "n")).valueOf()).to.equal(2);
+		});
+
+		it("can convert from Frequency", () => {
+			expect(Frequency(Frequency(2)).valueOf()).to.equal(2);
+			expect(Frequency(Frequency("4n")).valueOf()).to.equal(2);
+			expect(Frequency(Frequency(4, "n")).valueOf()).to.equal(2);
+		});
+
+		it("can convert from TransportTime", () => {
+			expect(Frequency(TransportTime(2)).valueOf()).to.equal(0.5);
+			expect(Frequency(TransportTime("4n")).valueOf()).to.equal(2);
+		});
+
+		it("can convert from Midi", () => {
+			expect(Frequency(Midi("C4")).valueOf()).to.equal(Frequency("C4").valueOf());
+			expect(Frequency(Midi(60)).valueOf()).to.equal(Frequency("C4").valueOf());
+			expect(Frequency(Midi(61)).valueOf()).to.equal(Frequency("C#4").valueOf());
+		});
+
+		it("can convert from Ticks", () => {
+			return Offline(({transport}) => {
+				expect(Frequency(Ticks(transport.PPQ)).valueOf()).to.equal(2);
+				expect(Frequency(Ticks("4n")).valueOf()).to.equal(2);
+			});
+		});
+	});
+
+	context("Eval Types", () => {
+
+		it("evaluates numbers as frequency", () => {
+			expect(Frequency("1").valueOf()).to.equal(1);
+			expect(Frequency("123").valueOf()).to.equal(123);
+			expect(Frequency(3.2).valueOf()).to.equal(3.2);
+		});
+
+		it("evaluates notation", () => {
+			return Offline(({transport}) => {
+				transport.bpm.value = 120;
+				transport.timeSignature = 4;
+				expect(Frequency("4n").valueOf()).to.equal(2);
+				expect(Frequency("8n").valueOf()).to.equal(4);
+				expect(Frequency(16, "n").valueOf()).to.equal(8);
+				transport.bpm.value = 60;
+				transport.timeSignature = [5, 4];
+				expect(Frequency("1m").valueOf()).to.equal(1 / 5);
+				transport.bpm.value = 120;
+				transport.timeSignature = 4;
+			});
+		});
+
+		it("evalutes hertz", () => {
+			expect(Frequency("1hz").valueOf()).to.equal(1);
+			expect(Frequency("2hz").valueOf()).to.equal(2);
+			expect(Frequency(4, "hz").valueOf()).to.equal(4);
+			expect(Frequency("0.25hz").valueOf()).to.equal(0.25);
+		});
+
+		it("evalutes ticks", () => {
+			return Offline(({transport}) => {
+				expect(Frequency(transport.PPQ, "i").valueOf()).to.equal(2);
+				expect(Frequency(1, "i").valueOf()).to.equal(transport.PPQ * 2);
+			});
+		});
+
+		it("evalutes transport time", () => {
+			expect(Frequency("1:0").valueOf()).to.equal(0.5);
+			expect(Frequency("1:4:0").valueOf()).to.equal(0.25);
+			// expect(Frequency("2:1:0").valueOf()).to.equal(0.25);
+		});
+
+		it("evalutes midi", () => {
+			expect(Frequency(48, "midi").valueOf()).to.be.closeTo(teoria.Note.fromMIDI(48).fq(), 0.0001);
+			expect(Frequency(69, "midi").valueOf()).to.be.closeTo(teoria.Note.fromMIDI(69).fq(), 0.0001);
+		});
+
+		it("evalutes hz", () => {
+			expect(Frequency(48, "hz").valueOf()).to.equal(48);
+			expect(Frequency(480, "hz").valueOf()).to.equal(480);
+		});
+
+		it("can convert notes into frequencies", () => {
+			expect(Frequency("C4").valueOf()).to.be.closeTo(teoria.note("C4").fq(), 0.0001);
+			expect(Frequency("D4").valueOf()).to.be.closeTo(teoria.note("D4").fq(), 0.0001);
+			expect(Frequency("Db4").valueOf()).to.be.closeTo(teoria.note("Db4").fq(), 0.0001);
+			expect(Frequency("E4").valueOf()).to.be.closeTo(teoria.note("E4").fq(), 0.0001);
+			expect(Frequency("F2").valueOf()).to.be.closeTo(teoria.note("F2").fq(), 0.0001);
+			expect(Frequency("Gb-1").valueOf()).to.be.closeTo(teoria.note("Gb-1").fq(), 0.0001);
+			expect(Frequency("A#10").valueOf()).to.be.closeTo(teoria.note("A#10").fq(), 0.0001);
+			expect(Frequency("Bb2").valueOf()).to.be.closeTo(teoria.note("Bb2").fq(), 0.0001);
+		});
+
+		it("handles double accidentals", () => {
+			expect(Frequency("Cbb4").valueOf()).to.be.closeTo(teoria.note("Cbb4").fq(), 0.0001);
+			expect(Frequency("Dx4").valueOf()).to.be.closeTo(teoria.note("Dx4").fq(), 0.0001);
+			expect(Frequency("Dbb4").valueOf()).to.be.closeTo(teoria.note("Dbb4").fq(), 0.0001);
+			expect(Frequency("Ex4").valueOf()).to.be.closeTo(teoria.note("Ex4").fq(), 0.0001);
+			expect(Frequency("Fx2").valueOf()).to.be.closeTo(teoria.note("Fx2").fq(), 0.0001);
+			expect(Frequency("Gbb-1").valueOf()).to.be.closeTo(teoria.note("Gbb-1").fq(), 0.0001);
+			expect(Frequency("Ax10").valueOf()).to.be.closeTo(teoria.note("Ax10").fq(), 0.0001);
+			expect(Frequency("Bbb2").valueOf()).to.be.closeTo(teoria.note("Bbb2").fq(), 0.0001);
+		});
+
+		it("can accomidate different concert tuning", () => {
+			FrequencyClass.A4 = 444;
+			expect(Frequency("C4").valueOf()).to.be.closeTo(teoria.note("C4").fq(FrequencyClass.A4), 0.0001);
+			expect(Frequency("D1").valueOf()).to.be.closeTo(teoria.note("D1").fq(FrequencyClass.A4), 0.0001);
+			FrequencyClass.A4 = 100;
+			expect(Frequency("C4").valueOf()).to.be.closeTo(teoria.note("C4").fq(FrequencyClass.A4), 0.0001);
+			// return it to normal
+			FrequencyClass.A4 = 440;
+		});
+
+	});
+
+	context("transpose/harmonize", () => {
+
+		it("can transpose a value", () => {
+			expect(Frequency("A4").transpose(3).toMidi()).to.equal(72);
+			expect(Frequency("A4").transpose(-3).toMidi()).to.equal(66);
+			expect(Frequency(440).transpose(-12).valueOf()).to.equal(220);
+		});
+
+		it("can harmonize a value", () => {
+			expect(Frequency("A4").harmonize([0, 3])).to.be.an("array");
+			expect(Frequency("A4").harmonize([0, 3]).length).to.equal(2);
+			expect(Frequency("A4").harmonize([0, 3])[0].toNote()).to.equal("A4");
+			expect(Frequency("A4").harmonize([0, 3])[1].toNote()).to.equal("C5");
+
+			expect(Frequency("A4").harmonize([-12, 0, 12])).to.be.an("array");
+			expect(Frequency("A4").harmonize([-12, 0, 12]).length).to.equal(3);
+			expect(Frequency("A4").harmonize([-12, 0, 12])[0].toNote()).to.equal("A3");
+			expect(Frequency("A4").harmonize([-12, 0, 12])[1].toNote()).to.equal("A4");
+			expect(Frequency("A4").harmonize([-12, 0, 12])[2].toNote()).to.equal("A5");
+		});
+	});
+
+	context("Conversions", () => {
+
+		it("can convert frequencies into notes", () => {
+			expect(Frequency(261.625).toNote()).to.equal(teoria.Note.fromFrequency(261.625).note.scientific());
+			expect(Frequency(440).toNote()).to.equal(teoria.Note.fromFrequency(440).note.scientific());
+			expect(Frequency(220).toNote()).to.equal(teoria.Note.fromFrequency(220).note.scientific());
+			expect(Frequency(13.75).toNote()).to.equal(teoria.Note.fromFrequency(13.75).note.scientific());
+			expect(Frequency(4979).toNote()).to.equal("D#8");
+		});
+
+		it("can convert note to midi values", () => {
+			expect(Frequency("C4").toMidi()).to.equal(teoria.note("C4").midi());
+			expect(Frequency("C#0").toMidi()).to.equal(teoria.note("C#0").midi());
+			expect(Frequency("A-4").toMidi()).to.equal(teoria.note("A-4").midi());
+		});
+
+		it("can convert hertz to seconds", () => {
+			expect(Frequency(4).toSeconds()).to.equal(0.25);
+			expect(Frequency("2hz").toSeconds()).to.equal(0.5);
+		});
+	});
+
+});
diff --git a/Tone/core/type/Frequency.ts b/Tone/core/type/Frequency.ts
index 9a420320..ed6a97cd 100644
--- a/Tone/core/type/Frequency.ts
+++ b/Tone/core/type/Frequency.ts
@@ -1,8 +1,10 @@
 import { getContext } from "../Global";
-import { intervalToFrequencyRatio } from "./Conversions";
+import { intervalToFrequencyRatio, mtof } from "./Conversions";
 import { ftom, getA4, setA4 } from "./Conversions";
 import { TimeClass } from "./Time";
-import { TypeBaseExpression } from "./TypeBase";
+import { TimeBaseClass, TimeBaseUnit, TimeExpression, TimeValue } from "./TimeBase";
+
+export type FrequencyUnit = TimeBaseUnit | "midi";
 
 /**
  * Frequency is a primitive type for encoding Frequency values.
@@ -12,11 +14,11 @@ import { TypeBaseExpression } from "./TypeBase";
  * Frequency(38, "midi") //
  * Frequency("C3").transpose(4);
  */
-export class FrequencyClass extends TimeClass<Hertz> {
+export class FrequencyClass<Type extends number = Hertz> extends TimeClass<Type, FrequencyUnit> {
 
 	name = "Frequency";
 
-	readonly defaultUnits = "hz";
+	readonly defaultUnits: FrequencyUnit = "hz";
 
 	/**
 	 * The [concert tuning pitch](https://en.wikipedia.org/wiki/Concert_pitch) which is used
@@ -33,12 +35,12 @@ export class FrequencyClass extends TimeClass<Hertz> {
 	// 	AUGMENT BASE EXPRESSIONS
 	///////////////////////////////////////////////////////////////////////////
 
-	protected _getExpressions(defaultUnit): TypeBaseExpression<Hertz> {
-		return Object.assign({}, super._getExpressions(defaultUnit), {
+	protected _getExpressions(): TimeExpression<Type> {
+		return Object.assign({}, super._getExpressions(), {
 			midi : {
 				regexp : /^(\d+(?:\.\d+)?midi)/,
 				method(value): number {
-					if (this._defaultUnits === "midi") {
+					if (this.defaultUnits === "midi") {
 						return value;
 					} else {
 						return FrequencyClass.mtof(value);
@@ -50,7 +52,7 @@ export class FrequencyClass extends TimeClass<Hertz> {
 				method(pitch, octave): number {
 					const index = noteToScaleIndex[pitch.toLowerCase()];
 					const noteNumber = index + (parseInt(octave, 10) + 1) * 12;
-					if (this._defaultUnits === "midi") {
+					if (this.defaultUnits === "midi") {
 						return noteNumber;
 					} else {
 						return FrequencyClass.mtof(noteNumber);
@@ -114,7 +116,7 @@ export class FrequencyClass extends TimeClass<Hertz> {
 	 * Frequency("C4").toMidi(); //60
 	 */
 	toMidi(): MidiNote {
-		return FrequencyClass.ftom(this.valueOf());
+		return ftom(this.valueOf());
 	}
 
 	/**
@@ -158,36 +160,36 @@ export class FrequencyClass extends TimeClass<Hertz> {
 	/**
 	 *  With no arguments, return 0
 	 */
-	protected _noArg(): Hertz {
-		return 0;
+	protected _noArg(): Type {
+		return 0 as Type;
 	}
 
 	/**
 	 *  Returns the value of a frequency in the current units
 	 */
-	protected _frequencyToUnits(freq: Hertz): Hertz {
-		return freq;
+	protected _frequencyToUnits(freq: Hertz): Type {
+		return freq as Type;
 	}
 
 	/**
 	 *  Returns the value of a tick in the current time units
 	 */
-	protected _ticksToUnits(ticks: Ticks): Hertz {
-		return 1 / ((ticks * 60) / (this._getBpm() * this._getPPQ()));
+	protected _ticksToUnits(ticks: Ticks): Type {
+		return 1 / ((ticks * 60) / (this._getBpm() * this._getPPQ())) as Type;
 	}
 
 	/**
 	 *  Return the value of the beats in the current units
 	 */
-	protected _beatsToUnits(beats: number): Hertz {
-		return 1 / super._beatsToUnits(beats);
+	protected _beatsToUnits(beats: number): Type {
+		return 1 / super._beatsToUnits(beats) as Type;
 	}
 
 	/**
 	 *  Returns the value of a second in the current units
 	 */
-	protected _secondsToUnits(seconds: Seconds): Hertz {
-		return 1 / seconds;
+	protected _secondsToUnits(seconds: Seconds): Type {
+		return 1 / seconds as Type;
 	}
 
 	/**
@@ -198,7 +200,7 @@ export class FrequencyClass extends TimeClass<Hertz> {
 	 * FrequencyClass.mtof(69); // returns 440
 	 */
 	static mtof(midi: MidiNote): Hertz {
-		return FrequencyClass.A4 * Math.pow(2, (midi - 69) / 12);
+		return mtof(midi);
 	}
 
 	/**
@@ -239,6 +241,9 @@ const noteToScaleIndex = {
  */
 const scaleIndexToNote = ["C", "C#", "D", "D#", "E", "F", "F#", "G", "G#", "A", "A#", "B"];
 
-export function Frequency(value, units?): FrequencyClass {
+/**
+ * Convert a value into a FrequencyClass object.
+ */
+export function Frequency(value?: TimeValue | Frequency, units?: FrequencyUnit): FrequencyClass {
 	return new FrequencyClass(getContext(), value, units);
 }
diff --git a/Tone/core/type/Midi.test.ts b/Tone/core/type/Midi.test.ts
new file mode 100644
index 00000000..15e0073e
--- /dev/null
+++ b/Tone/core/type/Midi.test.ts
@@ -0,0 +1,137 @@
+import { expect } from "chai";
+import teoria from "teoria";
+import { BasicTests } from "test/helper/Basic";
+import { Offline } from "test/helper/Offline";
+import { Frequency } from "./Frequency";
+import { Midi, MidiClass } from "./Midi";
+import { Ticks } from "./Ticks";
+import { Time } from "./Time";
+import { TransportTime } from "./TransportTime";
+
+describe("MidiClass", () => {
+
+	BasicTests(MidiClass);
+
+	context("Constructor", () => {
+
+		it("can pass in a number in the constructor", () => {
+			const midi = Midi(1);
+			expect(midi).to.be.instanceOf(MidiClass);
+			midi.dispose();
+		});
+
+		it("can pass in a string in the constructor", () => {
+			const midi = Midi("1");
+			expect(midi).to.be.instanceOf(MidiClass);
+			midi.dispose();
+		});
+
+		it("can pass in a value and a type", () => {
+			expect(Midi(128, "n").valueOf()).to.equal(36);
+		});
+
+		it("with no arguments evaluates to 0", () => {
+			expect(Midi().valueOf()).to.equal(0);
+		});
+
+		it("is evaluated in equations and comparisons using valueOf", () => {
+			// @ts-ignore
+			expect(Midi(1) + 1).to.equal(2);
+			// @ts-ignore
+			expect(Midi(1) + Midi(1)).to.equal(2);
+			// @ts-ignore
+			expect(Midi(1) > Midi(0)).to.be.true;
+			// @ts-ignore
+			expect(+Midi(1)).to.equal(1);
+		});
+
+		it("can convert from seconds", () => {
+			expect(Midi("0.1s").valueOf()).to.equal(3);
+			expect(Midi("0.05s").valueOf()).to.equal(15);
+			expect(Midi(0.05, "s").valueOf()).to.equal(15);
+		});
+
+		it("can convert from hertz", () => {
+			expect(Midi("440hz").valueOf()).to.equal(69);
+			expect(Midi(220, "hz").valueOf()).to.equal(57);
+		});
+
+		it("can convert from ticks", () => {
+			expect(Midi("1i").valueOf()).to.equal(67);
+			expect(Midi(2, "i").valueOf()).to.equal(55);
+		});
+
+		it("can convert from Time", () => {
+			expect(Midi(Time(0.01)).valueOf()).to.equal(43);
+			expect(Midi(Time("128n")).valueOf()).to.equal(36);
+			expect(Midi(Time(128, "n")).valueOf()).to.equal(36);
+		});
+
+		it("can convert from Midi", () => {
+			expect(Midi(Midi(2)).valueOf()).to.equal(2);
+			expect(Midi(Midi("64n")).valueOf()).to.equal(24);
+			expect(Midi(Midi(64, "n")).valueOf()).to.equal(24);
+		});
+
+		it("can convert from Frequency", () => {
+			expect(Midi(Frequency("C4")).valueOf()).to.equal(60);
+			expect(Midi(Frequency("64n")).valueOf()).to.equal(24);
+			expect(Midi(Frequency(64, "n")).valueOf()).to.equal(24);
+		});
+
+		it("can convert from TransportTime", () => {
+			expect(Midi(TransportTime(0.01)).valueOf()).to.equal(43);
+			expect(Midi(TransportTime("256n")).valueOf()).to.equal(48);
+		});
+
+		it("can convert from Ticks", () => {
+			return Offline(({transport}) => {
+				expect(Midi(Ticks(transport.PPQ)).valueOf()).to.equal(-24);
+				expect(Midi(Ticks("4n")).valueOf()).to.equal(-24);
+			});
+		});
+	});
+
+	context("Conversions", () => {
+
+		it("can convert frequencies into notes", () => {
+			expect(Midi(48).toNote()).to.equal(teoria.Note.fromMIDI(48).scientific());
+			expect(Midi(90).toNote()).to.equal(teoria.Note.fromMIDI(90).scientific());
+			expect(Midi("C#4").toNote()).to.equal("C#4");
+		});
+
+		it("can convert note to midi values", () => {
+			expect(Midi("C4").toMidi()).to.equal(teoria.note("C4").midi());
+			expect(Midi("C#0").toMidi()).to.equal(teoria.note("C#0").midi());
+			expect(Midi("A-4").toMidi()).to.equal(teoria.note("A-4").midi());
+		});
+
+		it("can convert midi to frequency", () => {
+			expect(Midi(60).toFrequency()).to.equal(teoria.Note.fromMIDI(60).fq());
+			expect(Midi(25).toFrequency()).to.equal(teoria.Note.fromMIDI(25).fq());
+			expect(Midi(108).toFrequency()).to.equal(teoria.Note.fromMIDI(108).fq());
+		});
+	});
+
+	context("transpose/harmonize", () => {
+
+		it("can transpose a value", () => {
+			expect(Midi("A4").transpose(3).toMidi()).to.equal(72);
+			expect(Midi("A4").transpose(-3).toMidi()).to.equal(66);
+			expect(Midi(69).transpose(-12).valueOf()).to.equal(57);
+		});
+
+		it("can harmonize a value", () => {
+			expect(Midi("A4").harmonize([0, 3])).to.be.an("array");
+			expect(Midi("A4").harmonize([0, 3]).length).to.equal(2);
+			expect(Midi("A4").harmonize([0, 3])[0].toNote()).to.equal("A4");
+			expect(Midi("A4").harmonize([0, 3])[1].toNote()).to.equal("C5");
+
+			expect(Midi("A4").harmonize([-12, 0, 12])).to.be.an("array");
+			expect(Midi("A4").harmonize([-12, 0, 12]).length).to.equal(3);
+			expect(Midi("A4").harmonize([-12, 0, 12])[0].toNote()).to.equal("A3");
+			expect(Midi("A4").harmonize([-12, 0, 12])[1].toNote()).to.equal("A4");
+			expect(Midi("A4").harmonize([-12, 0, 12])[2].toNote()).to.equal("A5");
+		});
+	});
+});
diff --git a/Tone/core/type/Midi.ts b/Tone/core/type/Midi.ts
new file mode 100644
index 00000000..8bae478b
--- /dev/null
+++ b/Tone/core/type/Midi.ts
@@ -0,0 +1,87 @@
+import { getContext } from "../Global";
+import { ftom, mtof } from "./Conversions";
+import { FrequencyClass, FrequencyUnit } from "./Frequency";
+import { TimeValue } from "./TimeBase";
+
+/**
+ *  @class Midi is a primitive type for encoding Time values.
+ *         Midi can be constructed with or without the `new` keyword. Midi can be passed
+ *         into the parameter of any method which takes time as an argument.
+ *  @constructor
+ *  @extends {Tone.Frequency}
+ *  @param  {String|Number}  val    The time value.
+ *  @param  {String=}  units  The units of the value.
+ *  @example
+ * var t = Midi("4n");//a quarter note
+ */
+export class MidiClass extends FrequencyClass<MidiNote> {
+
+	name = "Midi";
+
+	readonly defaultUnits = "midi";
+
+	/**
+	 *  Returns the value of a frequency in the current units
+	 */
+	protected _frequencyToUnits(freq: Hertz): MidiNote {
+		return ftom(super._frequencyToUnits(freq));
+	}
+
+	/**
+	 *  Returns the value of a tick in the current time units
+	 */
+	protected _ticksToUnits(ticks: Ticks): MidiNote {
+		return ftom(super._ticksToUnits(ticks));
+	}
+
+	/**
+	 *  Return the value of the beats in the current units
+	 */
+	protected _beatsToUnits(beats: number): MidiNote {
+		return ftom(super._beatsToUnits(beats));
+	}
+
+	/**
+	 *  Returns the value of a second in the current units
+	 */
+	protected _secondsToUnits(seconds: Seconds): MidiNote {
+		return ftom(super._secondsToUnits(seconds));
+	}
+
+	/**
+	 *  Return the value of the frequency as a MIDI note
+	 *  @return  {MIDI}
+	 *  @example
+	 * Midi(60).toMidi(); //60
+	 */
+	toMidi(): MidiNote {
+		return this.valueOf();
+	}
+
+	/**
+	 *  Return the value of the frequency as a MIDI note
+	 *  @return  {MIDI}
+	 *  @example
+	 * Midi(60).toFrequency(); //261.6255653005986
+	 */
+	toFrequency(): Hertz {
+		return mtof(this.toMidi());
+	}
+
+	/**
+	 *  Transposes the frequency by the given number of semitones.
+	 *  @return A new transposed MidiClass
+	 *  @example
+	 * Midi("A4").transpose(3); //"C5"
+	 */
+	transpose(interval: Interval): MidiClass {
+		return new MidiClass(this.context, this.toMidi() + interval);
+	}
+}
+
+/**
+ * Convert a value into a FrequencyClass object.
+ */
+export function Midi(value?: TimeValue, units?: FrequencyUnit): MidiClass {
+	return new MidiClass(getContext(), value, units);
+}
diff --git a/Tone/core/type/Ticks.test.ts b/Tone/core/type/Ticks.test.ts
new file mode 100644
index 00000000..8d974a89
--- /dev/null
+++ b/Tone/core/type/Ticks.test.ts
@@ -0,0 +1,190 @@
+import { expect } from "chai";
+import { BasicTests } from "test/helper/Basic";
+import { atTime, Offline } from "test/helper/Offline";
+import { getContext } from "../Global";
+import { Frequency } from "./Frequency";
+import { Ticks, TicksClass } from "./Ticks";
+import { Time } from "./Time";
+import { TransportTime } from "./TransportTime";
+
+describe("TicksClass", () => {
+
+	BasicTests(Ticks);
+
+	context("Constructor", () => {
+
+		it("can be made with or without 'new'", () => {
+			const t0 = Ticks();
+			expect(t0).to.be.instanceOf(TicksClass);
+			t0.dispose();
+			const t1 = new TicksClass(getContext());
+			expect(t1).to.be.instanceOf(TicksClass);
+			t1.dispose();
+		});
+
+		it("can pass in a number in the constructor", () => {
+			return Offline(({transport}) => {
+				const time = Ticks(1);
+				expect(time).to.be.instanceOf(TicksClass);
+				expect(time.valueOf()).to.equal(1);
+				time.dispose();
+			});
+		});
+
+		it("can pass in a string in the constructor", () => {
+			return Offline(({transport}) => {
+				const time = Ticks("1");
+				expect(time).to.be.instanceOf(TicksClass);
+				expect(time.valueOf()).to.equal(1);
+				time.dispose();
+			});
+		});
+
+		it("can pass in a value and a type", () => {
+			return Offline(({transport}) => {
+				expect(Ticks(4, "m").valueOf()).to.equal(transport.PPQ * 16);
+			});
+		});
+
+		it("with no arguments evaluates to 0 when the transport is stopped", () => {
+			return Offline(() => {
+				expect(Ticks().valueOf()).to.equal(0);
+			});
+		});
+
+		it("with no arguments evaluates to the current ticks when the transport is started", () => {
+			return Offline((context) => {
+				context.transport.start();
+				return atTime(0.29, () => {
+					expect(new TicksClass(context).valueOf()).to.equal(context.transport.ticks);
+					context.transport.stop();
+				});
+			}, 0.3);
+		});
+
+		it("is evaluated in equations and comparisons using valueOf", () => {
+			// @ts-ignore
+			expect(Ticks("1i") + 1).to.equal(2);
+			// @ts-ignore
+			expect(Ticks("1i") + Ticks("1i")).to.equal(2);
+			expect(Ticks("1i") > Ticks(0)).to.be.true;
+			expect(+Ticks("1i")).to.equal(1);
+		});
+
+		it("can convert from Time", () => {
+			return Offline(({transport}) => {
+				expect(Ticks(Time(2)).valueOf()).to.equal(transport.PPQ * 4);
+				expect(Ticks(Time("4n")).valueOf()).to.equal(transport.PPQ);
+				expect(Ticks(Time(4, "n")).valueOf()).to.equal(transport.PPQ);
+			});
+		});
+
+		it("can convert from Frequency", () => {
+			return Offline(({transport}) => {
+				expect(Ticks(Frequency(2)).valueOf()).to.equal(transport.PPQ);
+				expect(Ticks(Frequency("4n")).valueOf()).to.equal(transport.PPQ);
+				expect(Ticks(Frequency(4, "n")).valueOf()).to.equal(transport.PPQ);
+			});
+		});
+
+		it("can convert from TransportTime", () => {
+			return Offline(({transport}) => {
+				expect(Ticks(TransportTime(2)).valueOf()).to.equal(transport.PPQ * 4);
+				expect(Ticks(TransportTime("4n")).valueOf()).to.equal(transport.PPQ);
+			});
+		});
+
+		it("can convert from Ticks", () => {
+			return Offline(({transport}) => {
+				expect(Ticks(Ticks(transport.PPQ)).valueOf()).to.equal(transport.PPQ);
+				expect(Ticks(Ticks("4n")).valueOf()).to.equal(transport.PPQ);
+			});
+		});
+
+		it("can convert from an Object", () => {
+			return Offline(({transport}) => {
+				expect(Ticks({ "4n" : 2 }).valueOf()).to.equal(transport.PPQ * 2);
+				expect(Ticks({ "1n" : 1, "8t" : 2 }).valueOf()).to.equal(transport.PPQ * 4 + transport.PPQ * (2 / 3));
+			});
+		});
+	});
+
+	context("Quantizes values", () => {
+
+		it("can quantize values", () => {
+			return Offline(({transport}) => {
+				expect(Ticks("4t").quantize("4n").valueOf()).to.be.closeTo(transport.PPQ, 0.01);
+			});
+		});
+
+		it("can get the next subdivison when the transport is started", () => {
+			return Offline((context) => {
+				const transport = context.transport;
+				transport.start();
+				return atTime(0.59, () => {
+					expect(new TicksClass(context, "@1m").valueOf()).to.be.closeTo(4 * transport.PPQ, 1);
+					expect(new TicksClass(context, "@4n").valueOf()).to.be.closeTo(transport.PPQ * 2, 1);
+				});
+			}, 0.6);
+		});
+	});
+
+	context("Operators", () => {
+
+		it("can add the current time", () => {
+			return Offline((context) => {
+				context.transport.start();
+				return atTime(0.59, () => {
+					const now = context.transport.ticks;
+					expect(new TicksClass(context, "+4i").valueOf()).to.be.closeTo(4 + now, 0.01);
+					expect(new TicksClass(context, "+2n").valueOf()).to.be.closeTo(context.transport.PPQ * 2 + now, 0.01);
+					expect(new TicksClass(context, "+2n").valueOf()).to.be.closeTo(context.transport.PPQ * 2 + now, 0.01);
+					context.transport.stop();
+				});
+			}, 0.6);
+		});
+
+	});
+
+	context("Conversions", () => {
+
+		it("converts time into notation", () => {
+			return Offline(({transport}) => {
+				transport.bpm.value = 120;
+				transport.timeSignature = 4;
+				expect(Ticks("4n").toNotation()).to.equal("4n");
+				// expect(Ticks(1.5 * transport.PPQ).toNotation()).to.equal("2n + 4n");
+				expect(Ticks(0).toNotation()).to.equal("0");
+				// expect(Ticks("1:2:3").toNotation()).to.equal("1m + 2n + 8n + 16n");
+			});
+		});
+
+		it("converts time into samples", () => {
+			return Offline(({transport}) => {
+				expect(Ticks(transport.PPQ).toSamples()).to.equal(0.5 * getContext().sampleRate);
+			});
+		});
+
+		it("converts time into frequency", () => {
+			return Offline(({transport}) => {
+				expect(Ticks(transport.PPQ * 4).toFrequency()).to.equal(0.5);
+				expect(Ticks("2n").toFrequency()).to.equal(1);
+			});
+		});
+
+		it("converts time into seconds", () => {
+			return Offline(() => {
+				expect(Ticks("2n").toSeconds()).to.equal(1);
+			});
+		});
+
+		it("converts time into BarsBeatsSixteenths", () => {
+			return Offline(({transport}) => {
+				expect(Ticks("3:1:3").toBarsBeatsSixteenths()).to.equal("3:1:3");
+				expect(Ticks(4 * transport.PPQ).toBarsBeatsSixteenths()).to.equal("1:0:0");
+			});
+		});
+
+	});
+
+});
diff --git a/Tone/core/type/Ticks.ts b/Tone/core/type/Ticks.ts
index 84061587..e52ec013 100644
--- a/Tone/core/type/Ticks.ts
+++ b/Tone/core/type/Ticks.ts
@@ -1,7 +1,6 @@
-import { Context } from "../context/Context";
 import { getContext } from "../Global";
+import { TimeBaseUnit, TimeValue } from "./TimeBase";
 import { TransportTimeClass } from "./TransportTime";
-import { TypeBaseUnits } from "./TypeBase";
 
 /**
  * Ticks is a primitive type for encoding Time values.
@@ -14,7 +13,7 @@ export class TicksClass extends TransportTimeClass<Ticks> {
 
 	name = "Ticks";
 
-	readonly defaultUnits: TypeBaseUnits = "i";
+	readonly defaultUnits: TimeBaseUnit = "i";
 
 	/**
 	 * Get the current time in the given units
@@ -59,6 +58,6 @@ export class TicksClass extends TransportTimeClass<Ticks> {
 	}
 }
 
-export function Ticks(value: Time, units?: TypeBaseUnits): TicksClass {
+export function Ticks(value?: TimeValue, units?: TimeBaseUnit): TicksClass {
 	return new TicksClass(getContext(), value, units);
 }
diff --git a/Tone/core/type/Time.test.ts b/Tone/core/type/Time.test.ts
index 6f66f40b..e5439588 100644
--- a/Tone/core/type/Time.test.ts
+++ b/Tone/core/type/Time.test.ts
@@ -1,9 +1,11 @@
 import { expect } from "chai";
 import { BasicTests } from "test/helper/Basic";
-import { Offline } from "test/helper/Offline";
+import { atTime, Offline } from "test/helper/Offline";
 import { getContext } from "../Global";
-import { Tone } from "../Tone";
+import { Frequency } from "./Frequency";
+import { Ticks } from "./Ticks";
 import { Time, TimeClass } from "./Time";
+import { TransportTime } from "./TransportTime";
 
 describe("TimeClass", () => {
 
@@ -51,26 +53,26 @@ describe("TimeClass", () => {
 		});
 
 		it("can convert from Time", () => {
-			// expect(Time(Time(2)).valueOf()).to.equal(2);
+			expect(Time(Time(2)).valueOf()).to.equal(2);
 			expect(Time("4n").valueOf()).to.equal(0.5);
 		});
 
-		// it("can convert from Frequency", () => {
-		// 	expect(Time(Frequency(2)).valueOf()).to.equal(0.5);
-		// 	expect(Time(Frequency("4n")).valueOf()).to.equal(0.5);
-		// });
+		it("can convert from Frequency", () => {
+			expect(Time(Frequency(2)).valueOf()).to.equal(0.5);
+			expect(Time(Frequency("4n")).valueOf()).to.equal(0.5);
+		});
 
-		// it("can convert from TransportTime", () => {
-		// 	expect(Time(TransportTime(2)).valueOf()).to.equal(2);
-		// 	expect(Time(TransportTime("4n")).valueOf()).to.equal(0.5);
-		// });
+		it("can convert from TransportTime", () => {
+			expect(Time(TransportTime(2)).valueOf()).to.equal(2);
+			expect(Time(TransportTime("4n")).valueOf()).to.equal(0.5);
+		});
 
-		// it("can convert from Ticks", () => {
-		// 	return Offline(function(Transport) {
-		// 		expect(Time(Ticks(Transport.PPQ)).valueOf()).to.equal(0.5);
-		// 		expect(Time(Ticks("4n")).valueOf()).to.equal(0.5);
-		// 	});
-		// });
+		it("can convert from Ticks", () => {
+			return Offline(({ transport}) => {
+				expect(Time(Ticks(transport.PPQ)).valueOf()).to.equal(0.5);
+				expect(Time(Ticks("4n")).valueOf()).to.equal(0.5);
+			});
+		});
 
 		it("evalutes objects", () => {
 			return Offline(() => {
@@ -96,16 +98,17 @@ describe("TimeClass", () => {
 			expect(Time(2).quantize(8, 0.75).valueOf()).to.equal(0.5);
 		});
 
-		// it("can get the next subdivison when the transport is started", () => {
-		// 	return Offline(function(Transport) {
-		// 		Transport.start(0.1);
-		// 		return Test.atTime(0.69, () => {
-		// 			expect(Time("@1m").valueOf()).to.be.closeTo(2.1, 0.01);
-		// 			expect(Time("@4n").valueOf()).to.be.closeTo(1.1, 0.01);
-		// 			expect(Time("@8n").valueOf()).to.be.closeTo(0.85, 0.01);
-		// 		});
-		// 	}, 0.7);
-		// });
+		it("can get the next subdivison when the transport is started", () => {
+			return Offline((context) => {
+				const transport = context.transport;
+				transport.start(0.1);
+				return atTime(0.69, () => {
+					expect(new TimeClass(context, "@1m").valueOf()).to.be.closeTo(2.1, 0.01);
+					expect(new TimeClass(context, "@4n").valueOf()).to.be.closeTo(1.1, 0.01);
+					expect(new TimeClass(context, "@8n").valueOf()).to.be.closeTo(0.85, 0.01);
+				});
+			}, 0.7);
+		});
 	});
 
 	context("Operators", () => {
@@ -148,30 +151,30 @@ describe("TimeClass", () => {
 			expect(Time(2).toFrequency()).to.equal(0.5);
 		});
 
-		// it("converts time into ticks", () => {
-		// 	return Offline(function(Transport) {
-		// 		expect(Time("2n").toTicks()).to.equal(2 * Transport.PPQ);
-		// 		// floating point checks
-		// 		const bpmOrig = Tone.Transport.bpm.value;
-		// 		Tone.Transport.bpm.value = 100;
-		// 		expect(Time("0:1:3").toTicks()).to.equal(1.75 * Transport.PPQ);
-		// 		Tone.Transport.bpm.value = bpmOrig;
-		// 	});
-		// });
+		it("converts time into ticks", () => {
+			return Offline(({ transport }) => {
+				expect(Time("2n").toTicks()).to.equal(2 * transport.PPQ);
+				// floating point checks
+				const bpmOrig = transport.bpm.value;
+				transport.bpm.value = 100;
+				expect(Time("0:1:3").toTicks()).to.equal(1.75 * transport.PPQ);
+				transport.bpm.value = bpmOrig;
+			});
+		});
 
-		// it("converts time into BarsBeatsSixteenths", () => {
-		// 	return Offline(function(Transport) {
-		// 		expect(Time("3:1:3").toBarsBeatsSixteenths()).to.equal("3:1:3");
-		// 		expect(Time(2).toBarsBeatsSixteenths()).to.equal("1:0:0");
-		// 		// trailing zero removal test
-		// 		Transport.bpm.value = 100;
-		// 		expect(Time("0:1:3").toBarsBeatsSixteenths()).to.equal("0:1:3");
-		// 		expect(Time("14:0:0").toBarsBeatsSixteenths()).to.equal("14:0:0");
-		// 		expect(Time("15:0:0").toBarsBeatsSixteenths()).to.equal("15:0:0");
-		// 		Transport.bpm.value = 90;
-		// 		expect(Time("100:0:0").toBarsBeatsSixteenths()).to.equal("100:0:0");
-		// 	});
-		// });
+		it("converts time into BarsBeatsSixteenths", () => {
+			return Offline(({ transport }) => {
+				expect(Time("3:1:3").toBarsBeatsSixteenths()).to.equal("3:1:3");
+				expect(Time(2).toBarsBeatsSixteenths()).to.equal("1:0:0");
+				// trailing zero removal test
+				transport.bpm.value = 100;
+				expect(Time("0:1:3").toBarsBeatsSixteenths()).to.equal("0:1:3");
+				expect(Time("14:0:0").toBarsBeatsSixteenths()).to.equal("14:0:0");
+				expect(Time("15:0:0").toBarsBeatsSixteenths()).to.equal("15:0:0");
+				transport.bpm.value = 90;
+				expect(Time("100:0:0").toBarsBeatsSixteenths()).to.equal("100:0:0");
+			});
+		});
 
 	});
 
diff --git a/Tone/core/type/Time.ts b/Tone/core/type/Time.ts
index e7759881..6adb7fc8 100644
--- a/Tone/core/type/Time.ts
+++ b/Tone/core/type/Time.ts
@@ -1,6 +1,6 @@
 import { getContext } from "../Global";
 import { ftom } from "./Conversions";
-import { TypeBaseClass, TypeBaseExpression, TypeBaseUnits } from "./TypeBase";
+import { TimeBaseClass, TimeBaseUnit, TimeExpression, TimeValue } from "./TimeBase";
 
 /**
  * TimeClass is a primitive type for encoding and decoding Time values.
@@ -10,15 +10,16 @@ import { TypeBaseClass, TypeBaseExpression, TypeBaseUnits } from "./TypeBase";
  * @example
  * var t = Time("4n");//a quarter note
  */
-export class TimeClass<Type extends Seconds | Ticks = Seconds> extends TypeBaseClass<Type> {
+export class TimeClass<Type extends Seconds | Ticks = Seconds, Unit extends string = TimeBaseUnit>
+extends TimeBaseClass<Type, Unit> {
 
 	name = "Time";
 
-	protected _getExpressions(defaultUnit): TypeBaseExpression<Type> {
-		return Object.assign(super._getExpressions(defaultUnit), {
+	protected _getExpressions(): TimeExpression<Type> {
+		return Object.assign(super._getExpressions(), {
 			now: {
 				method: (capture: string): Type => {
-					return this._now() + new TimeClass(this.context, capture).valueOf() as Type;
+					return this._now() + new (this.constructor as typeof TimeClass)(this.context, capture).valueOf() as Type;
 				},
 				regexp: /^\+(.+)/,
 			},
@@ -42,8 +43,8 @@ export class TimeClass<Type extends Seconds | Ticks = Seconds> extends TypeBaseC
 	 * Time(21).quantize(2) //returns 22
 	 * Time(0.6).quantize("4n", 0.5) //returns 0.55
 	 */
-	quantize(subdiv: number | string | TimeObject, percent = 1): Type {
-		const subdivision = new TimeClass(this.context, subdiv).valueOf();
+	quantize(subdiv: number | Subdivision | TimeObject, percent = 1): Type {
+		const subdivision = new (this.constructor as typeof TimeClass)(this.context, subdiv).valueOf();
 		const value = this.valueOf();
 		const multiple = Math.round(value / subdivision);
 		const ideal = multiple * subdivision;
@@ -132,6 +133,11 @@ export class TimeClass<Type extends Seconds | Ticks = Seconds> extends TypeBaseC
 	}
 }
 
-export function Time(value?: Time, units?: TypeBaseUnits): TimeClass {
+/**
+ * Create a TimeClass from a time string or number.
+ * @param value A value which reprsents time
+ * @param units The value's units if they can't be inferred by the value.
+ */
+export function Time(value?: TimeValue, units?: TimeBaseUnit): TimeClass<Seconds> {
 	return new TimeClass(getContext(), value, units);
 }
diff --git a/Tone/core/type/TypeBase.ts b/Tone/core/type/TimeBase.ts
similarity index 80%
rename from Tone/core/type/TypeBase.ts
rename to Tone/core/type/TimeBase.ts
index 2527d04c..6a149a3f 100644
--- a/Tone/core/type/TypeBase.ts
+++ b/Tone/core/type/TimeBase.ts
@@ -1,75 +1,74 @@
-import { Tone } from "../../core/Tone";
 import { Context } from "../context/Context";
-import { getContext } from "../Global";
+import { Tone } from "../Tone";
 import { isDefined, isObject , isString, isUndef } from "../util/TypeCheck";
 
-interface TypeBaseClassOptions {
-	value?: TypeBaseClassValue;
-	units?: TypeBaseUnits;
-	context: Context;
-}
-
-type TypeBaseClassValue = string | number | TimeObject | TypeBaseClass<any>;
+export type TimeValue = Time | TimeBaseClass<any, any>;
 
 /**
- * TypeBase is a flexible encoding of time which can be evaluated to and from a string.
+ * The units that the TimeBase can accept. extended by other classes
+ */
+export type TimeBaseUnit = "s" | "n" | "t" | "m" | "i" | "hz" | "tr" | "samples" | "number";
+
+export interface TypeFunction {
+	regexp: RegExp;
+	method: (value: string, ...args: string[]) => number;
+}
+
+export interface TimeExpression<Type extends number> {
+	[key: string]: {
+		regexp: RegExp;
+		method: (value: string, ...args: string[]) => Type;
+	};
+}
+
+/**
+ * TimeBase is a flexible encoding of time which can be evaluated to and from a string.
  * @param  val    The time value as a number, string or object
  * @param  units  Unit values
  * @example
- * new TypeBase(4, "n")
- * new TypeBase(2, "t")
- * new TypeBase("2t")
- * new TypeBase({"2t" : 2})
- * new TypeBase("2t") + new TypeBase("4n");
+ * new TimeBase(4, "n")
+ * new TimeBase(2, "t")
+ * new TimeBase("2t")
+ * new TimeBase({"2t" : 2})
+ * new TimeBase("2t") + new TimeBase("4n");
  */
-export abstract class TypeBaseClass<Type extends Seconds | Hertz | Ticks> extends Tone {
+export abstract class TimeBaseClass<Type extends number, Unit extends string> extends Tone {
 
 	readonly context: Context;
 
 	/**
 	 * The value of the units
 	 */
-	protected _val?: TypeBaseClassValue;
+	protected _val?: TimeValue;
 
 	/**
 	 * The units of time
 	 */
-	protected _units?: TypeBaseUnits;
+	protected _units?: Unit;
 
 	/**
 	 * All of the conversion expressions
 	 */
-	protected _expressions: TypeBaseExpression<Type>;
+	protected _expressions: TimeExpression<Type>;
 
 	/**
 	 * The default units
 	 */
-	readonly defaultUnits: TypeBaseUnits = "s";
+	readonly defaultUnits: Unit = "s" as Unit;
 
-	constructor(context: Context, value?: TypeBaseClassValue, units?: TypeBaseUnits) {
+	constructor(context: Context, value?: TimeValue, units?: Unit) {
 		super();
 
 		this._val = value;
 		this._units = units;
 		this.context = context;
-
-		this._expressions = this._getExpressions(this.defaultUnits);
-
-		if (value instanceof TypeBaseClass) {
-			this.fromType(value);
-		}
-	}
-
-	static getDefaults(): TypeBaseClassOptions {
-		return {
-			context : getContext(),
-		};
+		this._expressions = this._getExpressions();
 	}
 
 	/**
 	 * All of the time encoding expressions
 	 */
-	protected _getExpressions(defaultUnit: TypeBaseUnits): TypeBaseExpression<Type> {
+	protected _getExpressions(): TimeExpression<Type> {
 		return {
 			hz: {
 				method: (value) => {
@@ -103,7 +102,7 @@ export abstract class TypeBaseClass<Type extends Seconds | Hertz | Ticks> extend
 			},
 			number: {
 				method: (value) => {
-					return this._expressions[defaultUnit].method.call(this, value);
+					return this._expressions[this.defaultUnits].method.call(this, value);
 				},
 				regexp: /^(\d+(?:\.\d+)?)$/,
 			},
@@ -153,12 +152,15 @@ export abstract class TypeBaseClass<Type extends Seconds | Hertz | Ticks> extend
 	 *  Evaluate the time value. Returns the time in seconds.
 	 */
 	valueOf(): Type {
+		if (this._val instanceof TimeBaseClass) {
+			this.fromType(this._val);
+		}
 		if (isUndef(this._val)) {
 			return this._noArg();
 		} else if (isString(this._val) && isUndef(this._units)) {
 			for (const units in this._expressions) {
 				if (this._expressions[units].regexp.test(this._val.trim())) {
-					this._units = units as TypeBaseUnits;
+					this._units = units as Unit;
 					break;
 				}
 			}
@@ -267,7 +269,7 @@ export abstract class TypeBaseClass<Type extends Seconds | Hertz | Ticks> extend
 	 * Coerce a time type into this units type.
 	 * @param type Any time type units
 	 */
-	fromType(type: TypeBaseClass<any>): void {
+	fromType(type: TimeBaseClass<any, any>): this {
 		this._units = undefined;
 		switch (this.defaultUnits) {
 			case "s":
@@ -279,7 +281,11 @@ export abstract class TypeBaseClass<Type extends Seconds | Hertz | Ticks> extend
 			case "hz":
 				this._val = type.toFrequency();
 				break;
+			case "midi":
+				this._val = type.toMidi();
+				break;
 		}
+		return this;
 	}
 
 	/**
@@ -327,17 +333,3 @@ export abstract class TypeBaseClass<Type extends Seconds | Hertz | Ticks> extend
 		return this;
 	}
 }
-/**
- * The units that the TypeBase can accept. extended by other classes
- */
-export type TypeBaseUnits = "s" | "n" | "t" | "m" | "i" | "hz" | "tr" | "samples" | "number";
-
-/**
- * The format of the type conversion expressions
- */
-export type TypeBaseExpression<T> = {
-	[key in TypeBaseUnits]: {
-		regexp: RegExp;
-		method: (value: string, ...args: string[]) => T;
-	};
-};
diff --git a/Tone/core/type/TransportTime.test.ts b/Tone/core/type/TransportTime.test.ts
new file mode 100644
index 00000000..f1ba0f5a
--- /dev/null
+++ b/Tone/core/type/TransportTime.test.ts
@@ -0,0 +1,184 @@
+import { expect } from "chai";
+import { BasicTests } from "test/helper/Basic";
+import { atTime, Offline } from "test/helper/Offline";
+import { getContext } from "../Global";
+import { Frequency } from "./Frequency";
+import { Ticks } from "./Ticks";
+import { Time } from "./Time";
+import { TransportTime, TransportTimeClass } from "./TransportTime";
+
+describe("TransportTimeClass", () => {
+
+	BasicTests(TransportTime);
+
+	context("Constructor", () => {
+
+		it("can be made with or without 'new'", () => {
+			const t0 = TransportTime();
+			expect(t0).to.be.instanceOf(TransportTimeClass);
+			t0.dispose();
+			const t1 = new TransportTimeClass(getContext());
+			expect(t1).to.be.instanceOf(TransportTimeClass);
+			t1.dispose();
+		});
+
+		it("can pass in a number in the constructor", () => {
+			return Offline(() => {
+				const time = TransportTime(1);
+				expect(time).to.be.instanceOf(TransportTimeClass);
+				expect(time.valueOf()).to.equal(1);
+				time.dispose();
+			});
+		});
+
+		it("can pass in a string in the constructor", () => {
+			return Offline((context) => {
+				const time = TransportTime("1");
+				expect(time).to.be.instanceOf(TransportTimeClass);
+				expect(time.valueOf()).to.equal(1);
+				time.dispose();
+			});
+		});
+
+		it("can pass in a value and a type", () => {
+			return Offline((context) => {
+				expect(TransportTime(4, "m").valueOf()).to.equal(8);
+			});
+		});
+
+		it("with no arguments evaluates to 0 when the transport is stopped", () => {
+			return Offline(() => {
+				expect(TransportTime().valueOf()).to.equal(0);
+			});
+		});
+
+		it("with no arguments evaluates to the current ticks when the transport is started", () => {
+			return Offline((context) => {
+				const transport = context.transport;
+				transport.start();
+				return atTime(0.29, () => {
+					expect(new TransportTimeClass(context).valueOf()).to.equal(transport.seconds);
+					transport.stop();
+				});
+			}, 0.3);
+		});
+
+		it("is evaluated in equations and comparisons using valueOf", () => {
+			// @ts-ignore
+			expect(TransportTime("1") + 1).to.equal(2);
+			// @ts-ignore
+			expect(TransportTime("1") + TransportTime("1")).to.equal(2);
+			expect(TransportTime("1") > TransportTime(0)).to.be.true;
+			expect(+TransportTime("1")).to.equal(1);
+		});
+
+		it("can convert from Time", () => {
+			expect(TransportTime(Time(2)).valueOf()).to.equal(2);
+			expect(TransportTime(Time("4n")).valueOf()).to.equal(0.5);
+		});
+
+		it("can convert from Frequency", () => {
+			expect(TransportTime(Frequency(2)).valueOf()).to.equal(0.5);
+			expect(TransportTime(Frequency("4n")).valueOf()).to.equal(0.5);
+		});
+
+		it("can convert from TransportTime", () => {
+			expect(TransportTime(TransportTime(2)).valueOf()).to.equal(2);
+			expect(TransportTime(TransportTime("4n")).valueOf()).to.equal(0.5);
+		});
+
+		it("can convert from Ticks", () => {
+			return Offline((context) => {
+				const transport = context.transport;
+				expect(TransportTime(Ticks(transport.PPQ)).valueOf()).to.equal(0.5);
+				expect(TransportTime(Ticks("4n")).valueOf()).to.equal(0.5);
+			});
+		});
+
+		it("can convert from an Object", () => {
+			return Offline(() => {
+				expect(TransportTime({ "4n" : 2 }).valueOf()).to.equal(1);
+				expect(TransportTime({ "1n" : 1, "8t" : 2 }).valueOf()).to.be.closeTo(2.333, 0.01);
+			});
+		});
+	});
+
+	context("Quantizes values", () => {
+
+		it("can quantize values", () => {
+			return Offline((context) => {
+				expect(TransportTime("4t").quantize("4n").valueOf()).to.be.closeTo(0.5, 0.01);
+			});
+		});
+
+		it("can get the next subdivison when the transport is started", () => {
+			return Offline((context) => {
+				const transport = context.transport;
+				transport.start();
+				return atTime(0.59, () => {
+					expect(new TransportTimeClass(context, "@1m").valueOf()).to.be.closeTo(2, 0.01);
+					expect(new TransportTimeClass(context, "@4n").valueOf()).to.be.closeTo(1, 0.01);
+				});
+			}, 0.6);
+		});
+	});
+
+	context("Operators", () => {
+
+		it("can add the current time", () => {
+			return Offline((context) => {
+				const transport = context.transport;
+				transport.start();
+				return atTime(0.59, () => {
+					const now = transport.seconds;
+					const quarterNote = 60 / transport.bpm.value;
+					expect(new TransportTimeClass(context, "+4i").valueOf()).to.be.closeTo(4 / transport.PPQ + now, 0.1);
+					expect(new TransportTimeClass(context, "+2n").valueOf()).to.be.closeTo(quarterNote * 2 + now, 0.1);
+					transport.stop();
+				});
+			}, 0.6);
+		});
+
+	});
+
+	context("Conversions", () => {
+
+		it("converts time into notation", () => {
+			return Offline((context) => {
+				const transport = context.transport;
+				transport.bpm.value = 120;
+				transport.timeSignature = 4;
+				expect(TransportTime("4n").toNotation()).to.equal("4n");
+				expect(TransportTime(1.5).toNotation()).to.equal("2n.");
+				expect(TransportTime(0).toNotation()).to.equal("0");
+				expect(TransportTime("1:0:0").toNotation()).to.equal("1m");
+			});
+		});
+
+		it("converts time into samples", () => {
+			return Offline((context) => {
+				expect(TransportTime(2).toSamples()).to.equal(2 * context.sampleRate);
+			});
+		});
+
+		it("converts time into frequency", () => {
+			return Offline(() => {
+				expect(TransportTime(2).toFrequency()).to.equal(0.5);
+			});
+		});
+
+		it("converts time into seconds", () => {
+			return Offline(() => {
+				expect(TransportTime("2n").toSeconds()).to.equal(1);
+			});
+		});
+
+		it("converts time into BarsBeatsSixteenths", () => {
+			return Offline(() => {
+				expect(TransportTime("3:1:3").toBarsBeatsSixteenths()).to.equal("3:1:3");
+				expect(TransportTime(2).toBarsBeatsSixteenths()).to.equal("1:0:0");
+			});
+		});
+
+	});
+});
diff --git a/Tone/core/type/TransportTime.ts b/Tone/core/type/TransportTime.ts
index 444a7109..83f29f0d 100644
--- a/Tone/core/type/TransportTime.ts
+++ b/Tone/core/type/TransportTime.ts
@@ -1,7 +1,6 @@
-import { Context } from "../context/Context";
 import { getContext } from "../Global";
 import { TimeClass } from "./Time";
-import { TypeBaseUnits } from "./TypeBase";
+import { TimeBaseUnit, TimeValue } from "./TimeBase";
 
 /**
  * TransportTime is a the time along the Transport's
@@ -21,6 +20,12 @@ export class TransportTimeClass<Type extends Seconds | Ticks = Seconds> extends
 	}
 }
 
-export function TransportTime(value: Time, units?: TypeBaseUnits): TransportTimeClass {
+/**
+ * TransportTime is a the time along the Transport's
+ * timeline. It is similar to Tone.Time, but instead of evaluating
+ * against the AudioContext's clock, it is evaluated against
+ * the Transport's position. See [TransportTime wiki](https://github.com/Tonejs/Tone.js/wiki/TransportTime).
+ */
+export function TransportTime(value?: TimeValue, units?: TimeBaseUnit): TransportTimeClass {
 	return new TransportTimeClass(getContext(), value, units);
 }
diff --git a/Tone/signal/Abs.test.ts b/Tone/signal/Abs.test.ts
index 46b37199..30f82698 100644
--- a/Tone/signal/Abs.test.ts
+++ b/Tone/signal/Abs.test.ts
@@ -47,4 +47,3 @@ describe("Abs", () => {
 	});
 
 });
-