(I guess these have been around online for a while but I just found out about them.)
Photographer James Mollison has been doing this series called "The Disciples" - composite images of concert-goers which highlight the ways music and fashion generate ad hoc tribal loyalties. Like so:
The Casualties concert, Blackpoool, UK, 2007
Bob Dylan concert, London, 2005
Dolly Parton concert, London, 2007
50 Cent concert, London, 2007
Merle Haggard concert, Huntsville, 2006
This sort of thing is obvious (and much-discussed) with really severely fashion-conscious subcultures (punks, goths, etc.). But, one thing I like about these photos is that they show how any popular-enough music movement can have its own aestheticized little cult. Like, I wouldn't necessarily think of any of those individual Bob Dylan fans as having particularly Dylanish style; but seeing them all together like that, it's clear that there's some sort of collective informing and affecting each individual.
The Guardian has
a bunch more of these in a fun quiz format - but in the answers section they mislabeled one which happens to be a band I really like (you can probably figure it out...).