The musical youths were never in Meiji Shrine: it's a shrine, not a park. They're next door in Yoyogi Park, and on the wide path from there towards Shibuya past the NHK complex.
Sorry, that's what I meant - didn't make meself clear enough on that one. Rock 'n' roll that's even audible in a shrine is pretty much unthinkable.
There was a pierced pavement artist near the railway bridge, but that's about the only sign we found of "alternative" culture. We were told very firmly that rebellious yoofs found setting up a sound system anywhere in the area, are now rapidly moved on by the police. But perhaps that's just the message they want to give to casual visitors!
And drat - You mean I missed some plastic food shops?? I love that stuff! Now there's one for the "must do" list if I ever get back there. Thanks for the tip Bushfiva.