A fun alternative is to build everything yourself for free, from scratch, as an app! Shameless plug: [1]

Some resources for getting started down this path: [2] [3] [4]

If anybody wants to chat about audio synthesis on iOS, feel free to get in touch :)

[1] https://github.com/aclissold/twyst

[2] http://jackschaedler.github.io/circles-sines-signals/

[3] http://mkonrad.net/projects/ios_audio_synth.html

[4] https://developer.apple.com/library/ios/documentation/MusicA...