(There's no video for Mac_Theremin yet. Please contribute to MR and add a video now!)
This application was once available for download from the BBC's website. Screen shot was found on Flickr
MAC_Theremin.sit (669.51 KiB / 685.58 KB)
3 / 2018-05-12 / c41210c22b69e8de3d08a17c97691ac06d15c078
It runs great under OS 9, running in classic mode in OS X it sometimes does not want to quit very cleanly.
Emulating this? It should run fine under: SheepShaver