I don't recall how the other brands work, but with Yamaha, if you take your hands off the keys and hit the transpose, nothing will happpen until you hit the accompaniament keys again. I've used this technique for years, merel by hitting a fill, then hit the keys to transpose.

Gary cool
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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.)