I film performers and club goers in clubs where music is playing. Not live music but recorded music where copyright has either already been paid for by the club or the performer.
Does the fact that they've paid for this copyright cover the sound of it appearing on their film?
Or does the club or performer have to pay twice? Once to play or perform and again to cover the film usage
There are actually two separate issues here. If you film some people who are in a club where the music is in the background, I think that under most circumstances this would be classed as incidental inclusion and therefore not an infringement of copyright. However when you film a performer who is signing either protected lyrics or using a backing track which is protected, the music is central to the performance, and so the issue of infringement may come into play. It then depends on the wording of the licence the singer or club has obrained. As there are many different licences available from organisations such as the PRS, you would need to check what they say. It most case, I would expect the licences to be fairly tightly constrained so that any secondary use (such as in your video) would be excluded. The PRS in particular are very hot on finding ways to increase their revenue, so if you are doing this as a business, you would be well advised to check with them.
I am filming in clubs big name djs purely to increase webtraffic - So effectively I could make a 2 min video using audio recorded from the camera, edit some cutaways of people dancing etc...
What about recording the DJ set (as WAV - good quality) and edit this with multiple camera angles? If you stipulate in the t&c that the videos imbedded on this site are for 'streaming only' not for download (ie like a radio / tv live broadcast )