Previously I owned B&W685 and they were terrible in the upper piano registers (too forward and thin).
I tried B&W PM1 and I think piano sounded fantastic on them, but this is a bit of a laid back speaker and the treble is tilted upward. It lends nice air and stringy definition of the piano. very nice for my taste. But I eventually returned the pair because I felt them a bit too laid back and I felt that the first order crossover crossed too high is too specific sounding.
I settled on the LS50 with best blend of faithful piano reproduction and lack of coloration.
I know how live piano sounds, I attend many concerts and take my daugter to classes. Sha has played Steinway, Bossendorfer, Feurich, uprights, etc. It’s very hard to describe what real piano sounds because there are many variables, like the condition and design of the piano, the room, the listener’s position and finally and most important the recording.
Most of classical recordings are far field and the there is too much room contribution. Most of jazz an especially pop is close miked and it often sounds like we never really hear it in a room or concert hall when played unamplified.
I would wholeheartedly recommend LS50 for piano reproduction. (with or without a sub)
B&W PM1 for a more musical and airy reproduction.