With its sleek rhythms, sophisticated arrangements, and intricate picking patterns, thrash metal has come to be regarded as a legitimate art form (by those in the know) in spite of its beginnings as a raw, guttural subgenre at the extreme end of the heavy-metal spectrum. Still, even for those who've caught on to the depth of bands like Metallica and Sepultura, Finnish cello quartet Apocalyptica has arguably shed the most light on the skill and finesse it takes to play its music. By supplanting guitars with cellos, Apocalyptica uncovers infinite levels of nuance that might otherwise remain hidden beneath guitar distortion, screaming vocals, and pounding drums. After listening to Apocalyptica's 1998 groundbreaking album, Inquisition Symphony, for example, worlds of subtlety become apparent when you can go back to the original versions. But rest assured that Apocalyptica's work is no soft-boiled interpretation meant for the classical concert hall. The music is played at complete intensity and rocks hard. Even sitting down, the band (which has included a drummer since 2005) works itself into a sweat that might take even more physical endurance than playing guitar, considering the arm angle that the cello requires.