A piano is a 3D object; it has long, vibrating string courses, and a large sound board. When you're playing a piano, sound is coming at your head from various angles. It changes depending on how you turn/move your head.
All of that is condensed into a single voltage signal and sent to a speaker.
A speaker is also a 3D object; it has various modes of vibration. With multiple speakers in a cabinet (even with just a mono signal, not talking about stereo), and reflections from walls and so on, you can hear different things in the 3D space.
These are not related; the speaker cabinet just won't reproduce the experience of playing a piano, or being right next to one. It reproduces its own sonic 3D signature.
Now if you're listening to a piano from a distance in a big hall, some of this matters less. Your head movements don't make much of a difference; it's almost just coming from a single point that could be represented by a single point source (one mic capture), panned into a stereo sound stage.
However: 99.9% of all piano music heard is not heard through a live piano directly. Make that several more nines if you're talking about someone who doesn't even play piano and occasionally hears something in a huge audience hall. It's heard recorded, and then played through a speaker.
Then let's say I want to play. If I'm trying to match something I've heard, it doesn't even make sense to take that physical piano into account. What I heard was a recording. I lose nothing by playing it out of a speaker.
If I want to play just for the joy of playing a physical object or something, that's a different story. But if I'm playing for a purpose other than that, the speaker loses nothing. And best of all? It's light and cheap!
> However: 99.9% of all piano music heard is not heard through a live piano directly.
That's obviously false for the individual who is a life-long, dedicated pianist, who listens to the piano in front of him or her for hours, daily, more than any other piano.
They would be short-changed by some piano synthesizer patch coming out of a pair of speakers.
> But if I'm playing for a purpose other than that,
In particular: the purpose of creating a quality recorded sound without the hassle of an acoustic space, with excellent microphones, placed expertly, going into quality preamps, and all that.
Synthesized and modeled sound makes it easier to produce (or fake, depending on your viewpoint) quality recorded music.
OP is clearly referencing the sum of all people who listen to a piano in a song. Not the "life-long, dedicated pianist"'s of the world. And to further that point, lots and lots of folks who play in touring bands do not haul a piano with them. They're usually using something like a Nord Stage.
All of that is condensed into a single voltage signal and sent to a speaker.
A speaker is also a 3D object; it has various modes of vibration. With multiple speakers in a cabinet (even with just a mono signal, not talking about stereo), and reflections from walls and so on, you can hear different things in the 3D space.
These are not related; the speaker cabinet just won't reproduce the experience of playing a piano, or being right next to one. It reproduces its own sonic 3D signature.
Now if you're listening to a piano from a distance in a big hall, some of this matters less. Your head movements don't make much of a difference; it's almost just coming from a single point that could be represented by a single point source (one mic capture), panned into a stereo sound stage.