These following jokes are provided at Instrument Jokes.
What do you get when you drop a piano down a mine shaft?
A flat minor.
What do you get when you drop a piano on an army base?
A flat major.
Why is an 11-foot concert grand better than a studio upright?
Because it makes a much bigger kaboom when dropped over a cliff.
Why was the piano invented?
So the musician would have a place to put his beer.
The audience at a piano recital were appalled when a telephone rang just off stage. Without missing a note the soloist glanced toward the wings and called, “If that’s my agent, tell him I’m working!”