Emerson, Lake and Palmer did a LP in the late 60s "Pictures from an Exhibition" a rock version of Mussorgsky and Ravel stuff, seem to remember there was a bit of debate about if they were rock 'purists' or not , one side said Cream (Clapton , Bruce, Taylor ) were the future and these guys were just jumping on the bandwagon , the other thought these guys were ace . myself I think at time I preferred these guys and thought Clapton and co. a bunch of posers , (Disreali Gears apart , which is okay I suppose)