Following on from FolkieDave, I'd like to get Eric Hobsbawm's view of it, although he does, I understand, favour jazz. On a Marxist view of history as being pretty much about economics, the human voice needs nothing physical more than reasonable health and a tolerable setting to sing. Cheapest instrument there is, in one way.

Doesn't need mains electricity, spare strings or tuning. Next up in cost/inconvenience scale are perhaps the tin whistle and harmonica and the shaky egg. And so it goes detouring through washboard and string bass through guitars and fiddles then squeezeboxen and Costalottas to such delights as Midi melodeons and the Eigenharp

Yes, there are swarms of youngsters playing instruments at festivals, and a good thing too. Just wondering how this may change as times get tighter.