I don't suppose the structure and concept of a "rock band" will ever totally die out. But it's a very different world now, and the golden age of youngsters learning guitar or bass or drums or keys — pursuant to the fraternity/brotherhood structure of a band — is fading. Make of that what ye will. In that "endangered species" spirit, I've been reading a lot of biographies and watching a lot of documentaries about rock bands that were written or made while the species was still relatively hearty. This Foo Fighters film, released in 2011 and now streaming on Netflix, is fascinating not just because of leader Dave Grohl's magnetic enthusiasm and talent. Also: A) Foo Fighters are an excellent and all-are-welcome synthesis of every hard rock, punk and melodic pop style to date, and B) Grohl is such an eloquent and outspoken activist fighting the tsunami of computer- and sample-based music now dominating charts.