Musical jokes, sophisticated and silly

Musical jokes:  these are pretty funny.  I especially like this one:

Q: How can you tell if a singer is at your door?
A: They can't find the key, and they never know when to come in.

These are cute for kids.
Here's a sample:
Why is a piano so hard to open?
(Because the keys are on the inside!)

Pianists

Q: Why is it pianists can open nearly any door?
A: Because their pianos have 88 keys!