It’s a few minutes before 8pm. Outside the Highline Ballroom in Chelsea, in lower Manhattan, scores of people are queuing in a desperate hope they’ll be able to get their hands on tickets for the gig taking place there tonight. Doors opened at 6, and the limited number of on-the-night tickets were snapped up instantly by those at the front of the queue. Two hours later, fans are still hanging around, asking, hoping for spares. That fervour is significant, as is the fact that Sixto Rodriguez, the headline act, has sold out the venue.