Hi, you can change play-modes using program change messages.
An other way to get unison in poly-61 which does not need an external controller:
– go to poly mode
– press hold
now press any keyboard key, if you want to layer multiple oscillators, press the same key up to six times.
– press ‘CHORD’
– now chord memory mode acts exactly like the unison mode. With the ModyPoly mod you can also use the LATCH switch to turn envelope retriggering on and off.