In 2017, Great Big Story talked to the creator of the Seinfeld theme, composer Jonathan Wolff (whose URL is amusingly https://seinfeldmusicguy.com), to tell the story behind the iconic song.
He says, "I have no idea how many themes we did for Seinfeld."
Every single episode had a new version of the music that Wolff improvised based on the rhythm of Jerry's opening monologue.
Here's an older interview with the now-retired musician:
image via TBS