Actually, a lot of what you're talking about sounds like a branch of
post rock headed by
Canadian moguls
Godspeed You Black Emperor! and
Dirty Three and also
Scotland's
Mogwai. Not very many vocals, though, but the same churning
epic melodies that usually denotes
classical music.
In fact, Godspeed You Black Emperor! did Adagio for strings on their EP Slow Riot for New Kanada. So it's been done, and done well.