Theremin MIDI is develop an idea of ordinary transistor Theremin instrument + MIDI interface.
I built an oscillator based on military grade transistors dedicated to the VFO constructions. The oscillator design is so simple. 2 transistors, two adjustable coil 680uH, and a few on a cross, resistors and capacitors :) and another one similarly for the volume VFO. But fun begins next when I started to build a MIDI interface for my VFO's.
First I built classic frequency converter directly to the MIDI based on ATmega. But I found that it is very accurate. Too much, really I not be able to control play. The scale was so thick that I had few octaves at a distance of 60 -70 cm from the antenna! Too dense to meaningfully play. Any changes to the code, in the frequency table not really help me. Occur problem witch losing accuracy :-|
So I thought that I must do it in other ways. I built an analog konwenter frequency to voltage. I configured range for my needs. I need get 2 and 3 octaves up, C-2 to C-5 which translates into the voltage 0-5V Bingo! It works pretty well, just fine-tune.
So pitch VFO, and VFO volume have analog converters frequency to voltage. I added VCA circuit for volume. Because Theremin also has audio output.
I wrote new code, converter incoming voltage to MIDI. Selected appropriately ranges, I added the possibility set up music note has start play. You can set the start of C2 or C3 or G # 3 or D-5 as you want in the range of octaves C-2 to C-6.
Scale in the distance 60cm to the antenna is the range of 2 octaves, from a preset note. This density 2 octaves allows always hit the note on air scale and can really play. Sounds are spread out well enough in space around the antenna.
Soon I add new video showing much improved final prototype.