I loved that theme song. It was thrilling and well constructed. I was stunned to find out later, that even though Issac Hayes had written and sold several popular songs before his own fame, Issac did not read music. He knew music, and hired others to make the necessary notations for all the background vocals, strings and brass.
Guess who else (very famous) never had to learn to formally read music? Macca, aka Paul McCartney. None of the Beatles ever learned to read or write proper notation. That’s what they hired George Martin for.
Elton John too. Maybe he had too much time on his hands and sticking that ,,,,never mind.