What are some alternatives?
When comparing AudioKit Synth One and G-Stomper Studio, you can also consider the following products
Sampulator - Make (and record) beats on your keyboard
KORG Gadget - KORG Gadget - From iOS to Mac. Music production software to help your musical imagination become reality.
Ableton - Music production software and hardware.
Caustic - Caustic is a music creation tool inspired by rack-mount synthesizers / samplers rigs.
Splice Beat Maker - Make and share beats in your browser
NanoStudio - NanoStudio is a recording studio for iOS, OS X and Windows.