Those who dance are considered insane by those who can’t hear the music.

George Carlin (1937-2008) American comedian

Book (1997), Brain Droppings, “Short Takes (Part 1)”
    (Source)

This phrase, or its meaning, pre-dates Carlin. Carlin himself attributes it to "Anon." in the epigraph of his next book, Napalm and Silly Putty (2001).

A version of it is often misattributed to Friedrich Nietzsche in this English form:

And those who were seen dancing were thought to be insane by those who could not hear the music.

While this English quotation does show up back into the 19th Century, there is no evidence that Nietzsche said it.

For more discussion, see:

• Quote Origin: Those Who Dance Are Considered Insane by Those Who Can’t Hear the Music – Quote Investigator®.
• Nietzsche Didn't Say That... But He Would've Agreed.

The phrase and its meaning are related to Thoreau's metaphor of "marching to the beat of a different drummer."