I've been using this app with a Theremini for a while now and it is a very good addition to the hardware. So if you have one, you should check out this app.
Get the most out of your Theremini with ThereMIDI a unique controller and patch editor.
ThereMIDI allows full real-tim control of the following parameters:
- VCO waveform, transpose, wavetable scan rate and more
- VCF cutoff frequency, resonance, filter type and key tracking
- Various modulations
- Advanced delay controls including effect mix, delay time and feedback
- Store and load presents on your iOS device
- Store presets to your theremini
ThereMIDI comes with a built in 16step mod sequencer. Sequence filter cutoff, resonance type and more. Even sequencing pitch is possible.
In this mode ThereMIDI converts CC data into MIDI notes making it possible to use the Theremini to play other synths. A built-in quantizer makes playing fun and easy to learn, users can choose from a variety of scales.
ThereMIDI costs $4.99 on the app store, and it's worth every penny