Paul, I'm still working on the onboard, vocal harmonies, and probably will try a comparison between the onboard system and TC Helicon Harmony-M on Sunday. So far, though, the Harmony-M seems significantly better in every respect.
Diki, Unfortunately, I didn't bother to listen to the right hand before it was automatically selected by the OTS, which was a mistake. That was the default volume and it's just one of the many things that's on my list of things to do before taking this keyboard on the road.
Cheers,
Gary

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PSR-S950, TC Helicon Harmony-M, Digitech VR, Samson Q7, Sennheiser E855, Custom Console, and lots of other silly stuff!
K+E=W (Knowledge Plus Experience = Wisdom.)