Thoughts on the most difficult instruments for speakers to reproduce?

Cello.
Hearing a cello in a quartet live vs recorded...
The recording never gives the real thing.
Massed violins are another tough one.
Agree about cymbals too.
(one of the able to hear reasons I just bought a $7000 disc player is hearing on a recording the clear sound of the brush hitting the cymbal, then the shimmer sound in response. Instead of the usual smear of noise)

I would chose voices and acoustic instruments, especially piano, violin and trumpets.

Back eons ago I was a rock and roll drummer and with some (but not all) well-recorded ride cymbals, you can "hear" the ping of the stick against the brass and "feel" the timbre of the cymbal vibrating.

Violins. High notes. 

kdude661,121 posts04-23-2018 11:49pmPiano,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.

100% agree.  In building components, I spent a few years on how to get the piano right.  I wanted to not only hear the wood of the piano and the hammers hitting the strings but I also wanted to hear the length and thickness of the strings and the attack and the decay.  It was a long road but now at the end, it was worth the effort.  Happy Listening.

Digital recordings are a terrible weakness of my system. Far too stucotto.