What are some alternatives?
When comparing NanoStudio and KORG Gadget, you can also consider the following products
G-Stomper Studio - G-Stomper Studio is a feature-packed, mobile music production tool.
DRC - Polyphonic Synthesizer - Cross-platform, virtual synthesizer for iOS that recreates the sound of classic, analog synths.
Sampulator - Make (and record) beats on your keyboard
Caustic - Caustic is a music creation tool inspired by rack-mount synthesizers / samplers rigs.
Music Maker Studio - Android app to make music and write songs with a multi track Midi sequencer.
Poison-202 - Vintage MIDI synthesizer for Mac and iOS