It is one of the signature songs of the 1960s, the moment when the “voice of a generation” (an epithet Bob Dylan always loathed) broke free of the strictures of folky protest to find himself in surrealistic poetry. Druggie anthem or search for the muse — it has been interpreted as both — “Mr Tambourine Man”’s most important legacy is that it threw open the possibilities of what pop, and specifically pop lyrics, could be. That it was covered almost immediately by The Byrds — in a rockier version as influential as Dylan’s acoustic original — only redoubles its impact.