From the Fillmore West in April of 1969, please enjoy the original five-piece line up of Procol Harum (with the great Matthew Fisher and Robin Trower) and a quite astounding live version of the title track from their amazing second LP "Shine on Brightly."
Objectively speaking, these guys may not have rocked as hard as anybody else of their era, but hands down nobody had a more majestic sound. And nobody ever achieved such a seamless mashup of Ray Charles and J.S. Bach.
That whole bootleg pictured above, BTW, is astounding. I've got a link for it somewhere; be nice to me and I'll find it and post it later today.