An example of how the wonderful harmoniser built into the Yamaha OSR SX900 can play external sounds - in this case a plugin in a DAW emulating a classic Oberheim synth.
Chord progressions are first set up in the CHORD LOOPER and a style set to play while HARMONY/ARPEGGIO is turned on.
One of the RIGHT keyboards are set up to use the HARMONISER *and* to send out on MIDI CH 2. This feeds a track in Ableton which is hosting the wonderful GFORCE OBERHEIM endorsed plugin which emulates 8 OBERHEIM SEM modules.
https://youtu.be/7Un6h6xMdnM