IMO, the problem with using a piano as a reference (generally) is that there are so many poorly recorded piano pieces. The piano must/has to be the hardest instrument to get recorded correctly to fully reproduce its the broad and nuanced (detail) sound capabilities, much more apparent live.
How does solo piano help you evaluate audio gear?
A pianist friend just recommended this article and pianist to me, knowing that I'm presently doing a speaker shoot-out. My question to you all is this:
How important is solo piano recordings to your evaluation of audio equipment -- in relation to, say, orchestra, bass, voice, etc.? What, specifically, does piano reveal exceptionally well, to your ears?
Here's the article:
https://positive-feedback.com/reviews/music-reviews/magic-of-josep-colom/