a really interesting topic. I'm still not quite sure how to best define "rock", what approach to take. imho there's fundamentally 2 different kinds of rock music:
rock, as in a composition: guitar, bass, drums as the focus, possibly but not necessarily a singer and any amount of other instruments. the rockband. this can musically be just about anything, and has great variation. from velvet underground to tortoise the rockband encompasses a huge array of western music from the 1950s onwards.
rock, as in rock music, the historical genre. rock is based in blues string instruments and rhythm section, and many of those principles were later altered and integrated into punk, metal, and many other spawns of rock music. this music is relatively similiar from a composition pov, but still has quite a variety of styles if you really think about it. black metal and progressive rock, but also psychedelic rock really push the boundaries of rock, so even then it's a pretty fluent genre.
is this rock music? it's certainly a rock formation, but has little/none of the blues roots in it. kind of difficult to tell, even for myself. genres only work insofar that music remains generic/formulaic
