This is a played-out musicians joke.

On his first to trip to New York City, a man decided to try and obtain tickets to the legendary Vladimir Horowitz. He got lost on his way to Carnegie Hall, so he asked a near-by taxi driver.
"Excuse me, sir. But how do you get to Carnegie Hall?"
The taxi driver, with a gleam in his eye, winked and replied, "Practice, my boy. Practice."