I’m not sure how this works on a standard Mac, but on my IPad, the Theremini when connected via USB shows up in the various Midi Menus for my different Synth apps, as a source and as a destination. I also use an app called Midibridge which is a more sophisticated Midi router and data manager to set up more complex connections.
On a regular Mac, if you have a USB Midi interface, the Theremin should show up in its manager as a selectable source and destination.
I bought a couple of “hockey puck” type USB Midi interfaces very cheaply on EBay that I use to make connections to external equipment. They seem to work just fine, and should work for your Mac as well.
There is no way currently to play the internal Theremini synth engine via Midi, but lots of synth and controller parameters can be wiggled, and each antenna sends a CC of your choice.
Currently everything only works on Midi channel 1, but this will probably change in a future update.
If you have an IPad, there is a preliminary editor available from the tech guys if you call and ask nicely 
It works in conjunction with an app called TB Midi ($5 I think) and gives you access to the sound editor and more, as well as the ability to name and save presets.
Hi,
on my iPad, i tried with Animoog for iPhone - but same as with OS X 10.6, no MIDI in or out was showing. I have asked Moog support but have not received any answer.
regards
g.a.
Hi g.a.
I’m not sure what your problem might be. My Theremini is working fine with Animoog (the IPad version).
It also shows up on my other apps, even the IMini, which has a fairly wonky Midi implementation.
I’m using an IPad Air, and have the Theremini connected to it with a mini USB to standard USB cable, which is plugged into the Apple USB adapter (USB to Lightning connector).
Which IPad are you using? I’ve read about some people having problems connecting when using non-Apple USB adapters or camera kit adapters for the older 30 pin devices. However, I bought a cheapie adapter off of Ebay as a backup, and it seems to work just as well as my much more expensive Apple adapter.
With the IPad Animoog, once the Theremini is connected, all I have to do is open Setup, and the Theremini is listed in both the Midi In and Midi Out menus.
Hope this helps!
I am having issues with the volume antenna. I play with a band. I calibrate and its fine. We play a bit then volume cannot be controlled. The auto mute is fine but I can’t Control the volume at all. I am new to the theremini world. Any help would be great. Thanks
Hi eightzero:
Make sure that you have the latest firmware update for your unit. There is a known bug that affects the operation of the volume antenna, and the latest firmware update (1.04) fixes this problem.
You can find it on the Moog site at the Theremini page, under downloads.
http://www.moogmusic.com/products/etherwave-theremins/theremini#downloads-tab
If you have any questions or problems, the techs at Moog can help you through the update procedure.
If you’ve got an IPad, you can plug the Theremini into it and use a Midi diagnostic program, like MIdi Toolbox, to see just what’s going on Midi-wise with your unit. This can be very helpful in weird situations. Since each antenna transmits a CC# (you can set which number you want for each) you can look at the data stream for each and see what is being transmitted. When properly calibrated, the volume antenna sends close to full code (127) with nothing near it, and as you move your hand closer to it, the output moves towards zero (no volume).
Hi,
i have found out why my Theremini did not show to output MIDI - wrong USB cable. I had that from an elder Panasonic digital film camera for loading still photographs without firewire. My Moog Dealer just tried another, seamingly more standard USB cable and the MIDI controller messages started to come out…
now as my Mac can receive MIDI from the Tehremini, i work on beiing also cable to get my iPad to communicate (Theremini Editor)
regards
G.Albrecht