Hi Henni
I used that set up in the late 80’s; I added a Midi pickup on my guitar which into the interface then into the Midi input of my Yamaha keyboard. My guitar was controlling the left hand of the keyboard, worked great. By changing Midi channels I was able to trigger a solo instrument sound.

I stopped using it because there was no way of playing melody lines, single notes and keep the chord in the left hand of the keyboard going. If I played melody chords; a chord with the melody as the highest note it did control the chords on the keyboard in full piano mode. Too much to think about; I went back to improving my keyboard playing.

John C.