Hi, Garfield Modular.
It usually took a day or two to make MIDI file.
The procedure is quite simple. Download MIDI files from the Internet and split it into 2 or 3 tracks to send each oscillator.
There is nothing between my modular and audio interface(Focusrite Scarlette), just putting 2 output from modular to 2 line input of Scarlette. I'm using Ableton live as a DAW. I do not mix it, but auto-mastering it in the masteringbox.com
I don't think I can deal with full orchestral symphonies now , they needs so many modules...
I hope to be able to do it if I can get more modules one day.
Thanks