The band known as Jethro Tull blew things wide open in 1972 with a single 43 minute song/concept album that hit #1 everywhere from Denmark to Australia to the Americas, even Vietnam. Which suddenly meant that Ian Anderson and the band could do pretty much anything they wanted career wise, including the release of a double album of (mostly) unreleased stuff from the previous four years and four albums of their career (so far). Living in the Past it was called and full of odd gems it was including a live version of Dharma For One which initially showed up as an instrumental on their first album but come the concert trails of 1970 had picked up some lyrics and otherwise expanded and evolved into a longer, wilder, more progressive beast indeed. The word gobsmacking comes to mind, though the drum solo does go on a bit.