I use a lot of voice registration changes with each song----sometimes 4 to 8 changes. The reason: When playing solo for up to 3 hours (instrumentally), piano alone gets a little stale for me. I’ll typically use piano on the first chorus, then on subsequent choruses of the tune, switch voices every 4 to 8 measures. That keeps the song interesting and customers seem to pay attention more, wondering what’s coming next.