How does solo piano help you evaluate audio gear?

@hilde45  I have found that solo piano recordings that I know well will reveal speaker aberrations pretty quickly.  I also use solo voice, hopefully, SATB, because I want nothing to do with a speaker that does not do voice right.  Not sure why, but I've also found  that good recordings of french horns can reveal aberrations that might otherwise go unnoticed.  If speakers pass these tests, then I go on to other speaker attributes.   I assume you are doing your evaluations at home in your own system with your own music.  Now that you are adept at optimizing speaker/room interactions, you are in a really good place to find a speaker that is going to do well for you. 

@hilde45, I use the ECM Schiff Beethoven recordings.  They are good recordings. Schiff used a Bosendorfer for some and a Steinway for others.  I think I can tell which piano he used on my system.  I took one of those recordings to an audition, and the speaker failed miserably to get the tonality right, though it sounded pretty good on orchestral works.  None of us were in the mixing room for a recording, so it is always a guess.  Assuming the recording engineer knew what he was doing, we make a judgement on what sounds "right."  

@hilde45 Thanks for starting this thread.  You've gotten some good stuff here from the AG all-stars.  I think I know what I am doing on auditioning speakers but I'm going to be rereading this the next time I audition any equipment.  A couple of things I would add.

You have to know your own ears.  You have to know what kinds of aberrations that you can hear right away and what types of recordings can reveal those aberrations. 

For me, solo piano gets very quickly to about 80% of what I need to hear (or not hear) in an audition. I've been able to reject some pricey speakers 30 seconds into a piano recording.  It reveals quickly speaker problems that may take a while for me to discern using other music. For that reason, if I am auditioning in a brick and mortar setting my first recording is piano. Other people may do better with other types of music. Know your ears!

Massed strings has been mentioned.  To be sure, a speaker that gets this right is a keeper.  This is a very high hurdle.   It is what you get for 80K that you can't get for 10K.

A few more words on French Horn.  A good system, especially a tube based system, can impart a richness and fullness to the horn that will make you melt into a pool of mush in your chair.  It's hard to describe, other than to say I am convinced that is how French Horns sound in heaven.

Certainly, voice is an imperative, and speaker manufacturers know this.  It is a lower hurdle for the manufacturer.   There are plenty of speakers that are credible on voice that I would not be happy with in my system. 

@mahgister ​​​​@hilde45 I have that Britten piece also.  I love it, and pretty much everything else Benjamin Britten wrote.

@mahgister,  I've agreed with pretty much everything you have said in this thread.   I will add a few comments/commentary.

When I am auditioning in a Brick and Mortar setting, time is limited and the variables are complex and not always controllable.   A speaker audition is a complex problem that is best solved by simplification.  Piano is a single, more or less full range instrument, whose harmonics are well known to most of us.  You can get to issues like tonal correctness across the audible spectrum and coherence/integration of drivers within a minute or two.  If a speaker fails this, you move on and haven't wasted 2 hrs on a speaker that might seem ok with other types of music, but 6 months and 20K later you want to get rid of.  I've personally not auditioned a speaker that passed the piano test and failed the voice test. My guess is there are none.   But piano won't tell you a lot that you need to know. Generally speaking, issues with imaging, soundstage width and depth, and dynamics, where many speakers can get very congested with a high volume complex orchestral work, may not be best discerned using solo piano.  So one certainly can't make a purchase decision based on piano alone, and I don't think anyone is really advocating that approach. 

 Piano is for me the first hurdle a speaker must pass.  I can reject a lot of speakers quickly using one or two well recorded and well known piano sonatas.  

What you say about the room is critical for anyone to understand.  But I won't take a pair of speakers home that don't sound right hoping the vendor had a lousy room.  Also, the caution you issue suggesting that people not go chasing expensive speakers until they are sure they have their room set up properly is extremely important.  Better speakers won't necessarily sound better in a room that is poorly treated and set up.  Relatively inexpensive speakers can sound mighty good in a room that is well set up. 

Along with absorbing  and diffusing surfaces, you mention reflective surfaces.  In my opinion, reflective surfaces and woefully underutilized.  Reflective surfaces that can convert early reflections into late reflections  is a trick I stumbled into by accident.  Proper use of reflective surfaces, in my experience, are an order of magnitude more effective in improving imaging and stage than absorbing surfaces.