Music plays a key role in people's lives, particularly teenagers and younger fans. How do people latch on to musical trends - such as hippies, goths, punks - and who encourages them there?
Groups such as So Solid Crew helped define hip-hop style
Right now hip-hop is the most powerful music on the planet.
For Soko Nzussi, a hip-hop fan from South Africa, its attraction is in the lyrics.
"It's about something that's happening in my life, and I can relate to it," they say.
"You just admire the art - the work that's gone into producing the song."
Meanwhile Sarah Lee, a hip-hop fan in New Zealand, loves the sense of belonging.
"You go into an environment, and people say, 'she's hip-hop.' And you connect straight away. It's amazing," she says.
Soko and Sarah are part of a global musical tribe, in this case hip-hop. But tribes exist for many types of music - punk, goth, reggae, rock - united by the music and its attendant identity, expressed in language and fashion.
In Japan, for example, fans of trance music have a very strong image, wearing garish clothes and mini dreadlocks.
"From my experience these people are 24/7," explained Nick Gluscom, a DJ in Tokyo.
"There's a really great word in Japanese, 'otaku', and it means someone who just gives their whole life to something, and just focus in on one thing. A lot of these guys and girls are like that.
Japanese rock fans are particularly devoted
"They live the whole side trance scene - they're not weekenders."
Paul Hodkinson, a sociologist who has written a study on identity and style amongst goth music fans, said that much research has shown many people who join groups such as punks, goths or rave were not necessarily very high-status in their usual environment, such as at school.
"Sometimes you'll find that people who were low status in the school environment will suddenly find this new group in which the things that they do are considered much more high-status, credit-worthy things," he said.
And he added that particularly noticeable was the role of relatively feminine men in the goth scene.
"At school they were either bullied or just not really noticed too much," he said.
"Suddenly they discover goth music, and they find themselves in an environment where actually, to be feminine as a man is rather valued, and suddenly girls are rather interested in you.
"I think it's an alternative set of values which renders people - who previously didn't have status - desirable."
London-based psychologist Lynette Rentoul explained that the influence which dictate which tribe people join can come from anywhere.
"Part of it is to do with some things that are very deep and personal - for example, how important is rebellion?" she said.
"How important is it to be very different from your parents, and therefore associate with groups that your parents would profoundly disapprove of?
"Others can take a more gentle route, where disapproval isn't the name of the game, but love, or you can want to identify with the wicked ones or the naughty ones."
Meanwhile, the relationship between the tribes and the idols they worship is also changing, at least partly through new technology.
British rock group Embrace, for example, established a tradition of arranging secret gigs with their fans in various locations - including the Angel Of The North and a scout hut - through the internet and text messages.
But now a clutch of bands are emerging who are taking this a step further, treating their fans with a respect of kinship that makes them virtually part of the group.
None have done so more successfully than The Others, who developed a fan club, the 853 Kamikaze Stage Diving Division, which followed them around the country while they were still looking for a record deal.
"Sometimes it wasn't the music that got us attention, it was the crowds," explained lead singer Dom Masters.
"The community, the devotion of the support - being able to sell out gigs on Tuesday and Thursday nights in wet winters.
"When you're up against bands of the same size, and they're not getting this kind of reaction, it makes the record companies prick up their ears."
He has a number on the band's website that fans can use to call, and a dedicated website message board with 2,200 members.
Masters explained that The Others took this approach because they did not like the deference other bands expected from their fans.
"Who's to say that because I stand on stage with a microphone and sing some lyrics, it makes me a higher-evolved species?" he said.
"You can't be. We're all the same, we're all human. What I try to do is break down those boundaries, so that it gives this idea that we're all one community."