This was a really bad problem with "piano" in the early stages of PG adding the instrument to RT's. It took a lot of versions to make the chord transitions completely smooth. I totally hear the rough transitions on voices - that is why I, and probably most people bury them in the mix - but that is what BGV's are meant for - we are not at the point where they can be solo'ed - I can take the oohs and ahhhh's into Logic ProX or ProTools and do fade in's on the start of the chord change too.