What are some alternatives?
NanoStudio - NanoStudio is a recording studio for iOS, OS X and Windows.
BlokDust - Join blocks together to build sounds with this web-based music making app.
AudioKit Synth One - Free & Open-source iPhone/iPad Synth 🎹
Sampulator - Make (and record) beats on your keyboard
Ramsophone - A generative art/music machine. (Be sure to refresh!)
Google Music Lab - Interactive experiments that use the Web Audio API