Traditional (not electric) piano have very inflexible tuning options. Human voice, violin, trombone, ... much better in this regard.

Even if you not thinking about "exotic"(at least for westerners) scales, but simple&clear western accords like just intonation.

https://en.wikipedia.org/wiki/Just_intonation#Singing_and_sc...

edit - music recommendation:

https://ziaspace.bandcamp.com/album/drum-n-space