Piano, defenatly piano.
Did you know that the piano was revultionary because it was the first keyboard instrument that you could change
it's volume by the strength that you press at? This is where his name comes from, in Italian: Piano (weak) Forte (strong), or piano in short.
The chambelo for example, an instrument that in many ways simillar to the piano, workd so when you press a note, a string is being pressed. therefore, you couldn't control it's volume.
technically you could, but by switching some levers at the time you play, which is a lot harder AND you couldn't do creshiendo (weak progressively turns strong), which is an importent part of the music.
Piano on the other hand, work's like this: when you press a note, a hammer hits a string, that way:

in this way, you could control the power the hammer hits the string, and therefore the volume.
It was invented btw in the beggining of the 18 century by an Italian man called Bartolomeo Christoferry.
I hope I expended your trivial knowledge.
So... Motzart or The Beatles? (you can say both, I have no problem with it.)