Thanks for all the advice above - it's a fantastic response.

I've used a MIDI device as input, but never as output. The penny has just dropped for me in the last few minutes that (I think) I can use conventional stereo audio output (panned to 0 and 127) PLUS I can send at least one channel to my puny MIDI keyboard - maybe two 'cos it's stereo. I used to sorta half know this stuff 5 years ago, so thanks for the refresher.

I have quite some time to prove the concept with all its hardware and software intangibles and I'm quite used to managing lots of audio wires.

So this is beginning to feel like a REAL solution.

I know from a choir director friend in Perth that church instruments have very fine electronics, but mine is strictly a secular activity.

NTed, will vear your excellent advice in mind. Have been on the receiving side of the baton for several years with a repertoire from high opera to Broadway. There's nothing more boring than sitting in a rehearsal area while SOME OTHER part of the group has to endure note-bashing. Hence my desire to note-bash at least four parts concurrently.

Many thanks again for the fine responses.

Regards, John