Also, most of the bands formed by young people in many countries now have similar drum kit, electric bass and lead guitar set-ups, perhaps singing in their own language but often in English with an American accent and pop/rock style - that IS reducing diversity.

Is that entirely true, WAV? And so what if it is? As an Anthropolohgist you should observe these things rather than passing scorn on them. People (ie Human Individuals like a you or a me) can do whatever they like (just as you do and I for that matter), this a simple act of choosing that enriches cultural diversity without apology. Otherwise from the available evidence I'd say there are plenty of yioung people the world over exploring their respective cultural idioms. Here's a particular favourite of mine from a few years back, just kids sharing music in a locker room...

http://www.youtube.com/watch?v=sv_LFxeK1Ik