A guy sees a sign outside a bar that says "Piano Player Wanted," so he goes in to apply. The bartender, who is desperate for a player, asks the man to play him something. The man sits down and plays some of the most beautiful music the bartender's ever heard.
"That was amazing" exclaims the bartender. "What was that called?"

"That was something I like to call 'A Weasel Ate My Balls.'"

"Oh. You know anything else?"

The guy plays another amazingly gorgeous piece. Impressed, the bartender applauds and asks what that one was called.

"It's called 'Would ya check out the tits on that one!'"

"Okay," says the bartender. "You can have the job. Just as long as you don't tell anyone the names of the songs."

So the guy begins working nights at the bar, playing to full houses every night, and, true to his word, never revealing the titles of the songs. One night, though, he takes a break to go to the bathroom and forgets to zip up his pants afterwards and his schlong is hanging out. A patron notices and approaches him.

"Do you know your pants are unzipped and your thing is hanging out?"

"Know it?" says the piano player. "I wrote it!"