I would guess most experienced, singing, arranger players would say go lightly with the harmony. Doing solo gigs with the SX 900, I use it sparingly----mainly on songs known for two-part harmony in particular parts of the song. It’s an attention getter, when used that way. I’ve had good luck singing my own pre-recorded harmony parts, mixing it to a wav file, along with the backing track, and playing it via the keyboard’s “player” function, all the while, singing the melody line. That takes a lot of preparation, but it works out better at times.