Scene where Steve Martin's character dances to music on the radio

Question

Maybe I just don't understand enough about pop culture to get this reference in The Jerk. Basically, Navin (Steve Martin's character), who seemed to have trouble feeling the rhythm of music his family played, was very impressed with this music he heard on the radio. He started tapping to the beat and snapping his fingers and said the following:

"It's unbelievable! I've never heard music like this before! It speaks to me!"

And then his mother was about to say something to him but his father stopped her:

"Let him go...".

This is meant to be a joke, but I don't understand it. Anyone care to explain?

Here's that scene on YouTube.

Answer 1

At this point in the film, we've seen that he can't hit the rhythm of the blues. However, when he hears the very stereotypically "White" music for the first time in his life it clicks, and he feels the music. This is a "joke" built on the stereotypes of white music vs. black music, balanced with Navin not knowing he was white until he hears this music...exemplified by him exclaiming:

"You, mean I'm going to stay this color?"

Answer 2

It's a spoof on cultural stereotypes. Being raised by a black family, he never picked up any rhythm in his blood. They don't have the heart to tell him, but in his own mind he has great rhythm. But as the audience can see, he is terrible. It's one of the many reasons he is a "Jerk" in the movie.