Gregorian chants generally don't have too much in common with rock music. Sure, sometimes they set a brooding tone in an intro to a doom metal song, but rockers generally scream, growl, wail or sing.

In the cool, dark room, an ethereal sound fills the air, a harmonic blend of harpsichord and dreamy chants. The music is punctuated by more music: a guitar strum, the sound of a flute, drumbeats. But ...