back in the 80's Led Zeppelin was notoriously stingy with their music. when Cameron Crowe asked them for a song they said yes but it could not be anything off of Led Zeppelin 4. they changed it to Kashmir and liked the final results because it showed how clueless Rat really was.You ever notice the song on the radio was Kashmir when they cut to Rat and Stacy in the car? That's Physical Grafitti. Always wondered if they did that on purpose or just a screw up only Zepplin fans would notice.