The best alternatives to Theremin are No Lick, Yume, and Visual Beat. If these 3 options don't work for you, we've listed a few more alternatives below.
What do you think of Theremin?
AssemblyAIโ Speech-to-Text API with superhuman accuracy
Holon is an auditive mixed reality app that uses IoT data and biomusicological principles to let you create synth music with your physical activities. Supports Bose AR Beta! Apple Watch app, S3 or newer. Now with bonus pro feature: Ableton Link.
AirSynth enables anyone to make cool musical sounds with their hands! Using the latest depth sensing camera technology in your device, AirSynth allows you to synthesize music simply by holding your hands in the air.