I just bought a Steinway which sounds like a banjo.

Ah, but there are Hamburg Steinways and New York Steinways.

Is that like British speakers vs. American, or like East Coast sound vs. West Coast?

Terminology is wonderful, in the studio every producer, engineer and musician must communicate with terminology that is meant to relate a feeling in the sound. Very rarely will a musician say I need 605hz taken down 3.5 db but it does happen sometimes.
Pianos are very hard to record because of phasing (a term not on your list) when you have a lid on the piano there are phasing issues by definition, when you have 2+ mics out you have phasing issues by definition. Creative people come up with new terms so an engineer can turn that feeling into technical manipulation of the signal.

I am a professional pianist and I feel that piano is one of the hardest instruments to really reproduce.  Maybe I'm biased because its my instrument but I think because of its enormous range and complexity of interacting overtones, not just with sympathetic vibrations or the strings but interactions with the soundboard and cabinet, it's really hard to get it right.  That being said, I feel that 9 times out of 10, it's the recording that gets it wrong, not the speakers or the electronics.  Bad mic placement, bad EQ, bad mic choice all contribute to pianos not sounding like pianos.  One of the micing techniques that has become en-vogue is to put two ribbon mics less than an inch away from the strings.  Who listens to a piano like that with their ear inside the lid inches away from the strings!  I'm sure speakers and electronics can contribute to the timbre of a piano from being off, but there are a whole slew of bad things that can happen before that sound reproduction gets to the hi-fi.

Maybe you should have just bought a Banjo and saved a whole hell of a lot of money

X @ replicnt6, what a shame for making such a mistake! Ahhhh .... Can I try the subjectivity game? For me they are adjectives! Joke. Shame.
Let’s get back to the sound ... Obviously there is no system that can perfectly reproduce the sound of a piano. The same happens with color reproduction in print. Perfect color reproduction is not possible. Despite this, in this sector they do everything possible to get as close as possible to the ideal result. Measure everything possible and agree on certain standards. Converting RGB to CMYK is already a huge problem, because the CMYK space doesn’t have its own light, so it relies on an auxiliary light. More or less the problem of space when playing an instrument on a speaker that has its own space. A similar problem is faced by those who produce a Fazioli who have to grasp a lot of objective aspects, and then, right at the end, there is a small space for the "character" which is part of the differences between a great Yamaha, Steinway, Fazioli and so on. But in this area it seems they don’t want to define any stadard. It would be easy to agree even on multiple stadards. Imagine defining 128 recording standards, using different microphones, media and recording approaches in order to have the masters of something like a "history of audio recording" in controlled environments. You can do a lot of things with something like this. It is also possible to use this material to train neuronal networks in order to improve the digitization of old recordings. Now imagine you have a Steinway Spirio (it can mechanically record itself almost perfectly so you have the same live performance at your disposal as many times as you want), 128 recordings of the same Stainway and the most neutral amplification possible, and a new pair of Speakers in one space that matches the size of the recording space. Now you can start comparing the original with the master recordings played on the new speakers and learn a lot. If you want to agree on standards in an industry, you can raise millions so you can really do something like this with multiple music instruments. In other sectors they always do. In the meantime I have a pair of $ 10,000 speakers that sound much, much, much worse, from every point of view, than my father’s 1986 Bose 505, worth $ 300 driven by a cheap denon. It does not make any sense. P.S. Yes i sent them even back to the manufacturer and they come back almost identical.