Auxy Music Studio - Auxy brings real music creation to iPhone in a simple and inspiring format.
Logic Pro X - Music production.
Sampulator - Make (and record) beats on your keyboard
AudioKit Synth One - Free & Open-source iPhone/iPad Synth 🎹
Ramsophone - A generative art/music machine. (Be sure to refresh!)
Splice Beat Maker - Make and share beats in your browser