Company Audiobus Pty Ltd created these great apps:
Audiobus 2, Audiobus Remote, Audiobus: Mixer for Music Apps, AudioKit FM Player 2: DX Synth, AudioKit Digital D1 Synth, LE01 | Bass 808 Synth + AUv3, AudioKit Retro Piano, LE05: Digitalism 2000 + AUv3, VHS Synth | 80s Synthwave, and others..