Thoughts on the most difficult instruments for speakers to reproduce?

Piano,Piano,and Piano.

When you have a system that gets all aspects of the Piano correct everything thing else will be there,with maybe the exception of the lwr Organ notes being totally realistic.

Kenny.

Piano for me. I have heard very expensive $0.5 million systems sound perfect, see: https://forum.audiogon.com/discussions/2c-hifi-epiphany-worlds-best-system. Until you play a grand piano. No speaker IMHO will reproduce grand piano lifelike. Some come close, but, at the end of the day it is very apparent you are listening to recorded music.

piano

Let's hear why piano is so specifically hard to reproduce.

I'd say some reasons:

1. Spans more of the frequency range than most instruments, hence has wider scope to show weaknesses in upper and lower areas of the speaker design.

2. Has a combination of percussive yet soft quality (a soft "hammer" striking hard wires) that is so easy to miss, either becoming too fuzzy or soft, or too hard and artificial.

3.  It seems extremely hard to both record and reproduce the BODY of the piano sound.  In real life the whole instruments seems to be in play, and you can "feel" the weight of the vibrating strings and the soundboard, body of the piano.  On recordings and through hi fi systems piano becomes a set of detached, floating keys being struck...as if severed from and preserved, the rest of the instrument thrown away.

Piano.