When Pink Floyd first formed, David Gilmour and Roger Waters didn’t think about starting progressive rock from the ground up or anything. Gilmour only came on as a sideman for the first few months after Syd Barrett could no longer tour, and even when they did end up finding their sound, it was a lot more unique to them whenever they hit upon a song like ‘Echoes’ compared to the long exercises that a band like Yes or Emerson, Lake and Palmer wou…