This isnt quite hi-fi related - though could be, and it doesn't have to be digital either, but could be.

I am currently experimenting with DAWs - right now it's Reaper, and Midi. I have a specific project right now which is to try to get a working realisation of Bach's Contrapunctus I so that I can isolate individual tracks, and also play along with the whole and at tempos which are possibly variable. Simple play along can be achieved by using a recording, such as that by the Emerson quartet, but it would be good to be able to have better control - and the Emersons do play at a reasonable speed, but perhaps a tad too fast for amateurs trying to learn the intricacies of the pieces.

Midi has been around for a long while, but it seems that although there are many people out there who must have used it, there are even more who haven't, and many musicians don't really know how it works.

So far I have managed to get keyboard input to an iPad via a Roland UM-1 interface - that's running to Garageband, but no output back to my Yamaha keyboard. I think that's because Garageband doesn't do Midi output.

I also have downloaded midi files for the Contrapunctus - though there is a gotcha there. Some are just audio files, which is not what is needed. However, there are midi files which will drive a midi controller, and then can drive a midi synthesizer. Ideally what I'd like to achieve immediately is getting the midi controller (for example midi file+ Reaper DAW) to drive the hardware synthesizer in my keyboards. Reaper appears to be really good as it can treat tracks as audio, midi or ... whatever - very flexible. Reaper - https://www.reaper.fm/

Of course Reaper isn't the only DAW which may be good, but there is a good trial, and even the licensed version should be affordable. I could look at other DAWs - perhaps even Logic Pro, which is more expensive, but right now the aim is not to spend a fortune, and yet get something which works, and shows feasibility.

I've got as far as getting Reaper to produce sounds by using some software synthesizers, but I really would like to drive the keyboards - partly because the sound output would be loud eough, and partly just to prove I can do it.

I have looked at a few Youtube videos to find clues - some are better than others. I'm gradually homing in on solutions, but I'm not there yet.

Has anyone else trod these paths before - though there are many paths - which may, or may not, lead to the desired end result?