strange as it sounds, I think those combinations could work
Rush could play whatever the hell they wanted to and it would be great, Mylie screaming some death metal might be interested, I'd rather hear her growl though. And Opeth scoring a ballet is not that big of a stretch since they're a bunch of kweerfags anyway - lol Look at what happened to Savatage for example, they did a side project in a totally different orchestral style "Trans Siberian Orchestra" and its been far more successful than anything they ever did as a straight ahead metal band.
My favorite band "Cannibal Corpse" I dont really think would be able to switch genres drastically and pull it off though, but I've always thought it would be interesting for them to take a more classic rock/metal song with appropriate subject matter for them and remake it in more of a death metal style - for example Alice Cooper's "Cold Ethyl" not really a death metal song at all other than the lyrics and subject matter would make it interesting if it was brought in the right direction with some down tuned heavy riffing and double bass blast beats.
