Sigur Rós’ second record—their first to be widely heard outside their native Iceland—is one of those epochal, game-changing albums that redefined what is possible in rock music. In this case, it proved that a neoclassical, shoegazing post-rock band specializing in glacially paced 10-minute movements sung in a made-up, indecipherable dialect could attract a mass audience and become one of the most influential alt-rock groups of their generation. Ágætis Byrjun delivers one weighty moment after another: sonar-pinged arias that gradually accrue enough force to shift tectonic plates (“Svefn-F-Englar”); meditative piano ballads that erupt into shrieking symphonic psychedelia ("Viðrar vel til loftárása"); choral sing-alongs that sound like Christmas in heaven (“Olsen Olsen”). But for all of his band’s grandiose gestures, Jónsi Birgisson's crystalline, androgynous coo turns Ágætis Byrjun into an intensely intimate experience. Even if you can’t understand what he’s saying, his vulnerable voice has the uncanny power to tap into your most repressed emotions and deep-seated bittersweet memories.