If you want decent harmony stay away from Yamaha. They don't even know what decent harmony sounds like. I produced a Cd with a rented PA 800 and the harmonies were good. The 900 took away one of the voices but I'm sure it's still good.
Here's one of my songs with the Korg harmonies.

https://youtu.be/wHgUfF9wDL4

God Bless,
Don
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God Bless,
Don