koel/app/Repositories/ArtistRepository.php

<?php

namespace App\Repositories;

use App\Models\Artist;
use App\Models\Song;

class ArtistRepository extends AbstractRepository
{
    public function getModelClass(): string
    {
        return Artist::class;
    }

    public function getNonEmptyArtistIds(): array
    {
        return Song::select('artist_id')
            ->groupBy('artist_id')
            ->get()
            ->pluck('artist_id')
            ->toArray();
    }
}