" MIDI really needs an update (higher baud rate, single cable bidirectionality, audio channels, etc.) but good luck getting manufacturers to further commodify their products." - Dewster
MIDI is too slow, as you say - There are other interfaces / protocols being used for music data - one of the simplest is MIDI over USB, here one can stream multiple midi "ports" at high speed, the driver in the PC "sees" these as independent MIDI ports, and it is possible for example to have pitch CC messages being streamed continuosly to one port, Volume CC to another, etc..
None of which helps you to drive any MIDI instruments however - the only way to get the MIDI data to play a synth is to stream this data to a software synth specifically created to accept it.. It does however allow one to accurately record a theremin performance in MIDI form.
"In a future version, (pending I get a boost in enthusiasm for programming again) I could add a continuous pitch control tracking mode, where 14-bit pitch bend data (with a target bend range of only one semitone)" - Randy George
I am puzzled by why the bend range is limited to one semitone - I have MIDI gear which happily accepts +/- 2 semitone bend, which gives a perfectly acceptable 1/10th cent resolution.. I agree that going lower resolution than this starts to become audible (produce zipper type effects, particularly as the MIDI update speed is slow)
I personally do not think that single-port MIDI is of any real use with theremins - I also think that, for any digital control data sheme to be useful with theremins, it will require "reciever" instruments specifically designed or adapted to take theremin data.
What one (IMO) really needs is theremin with multiple input and output MIDI ports, and probably a USB port (Or alternatively only a USB port "emulating" multiple MIDI ports) - And one needs "reciever" instruments which accept these multiple MIDI ports and behave in a different way to conventional MIDI appliances - In particular, "Note-On" must not "retrigger" anything, it must simply update the pitch against which bend data is referenced - and volume would be determined soley by CC messages. If the Note-on/off (perhaps with a snapshot value of the volume value embedded in the velocity data) was sent one one port, this could then be directed to any standard MIDI gear..
The "transmitting" theremin should ideally be able to replay the data it sent. With the above scheme it would be possible to use MIDI recording / sequencing software without modification.