When they debuted with the feedback-drenched single "Upside Down" in 1984, Scotland's Jesus & Mary Chain revolutionized the British music scene, taking the forefront of the so-called "dream-pop" movement that would influence countless bands, including My Bloody Valentine, Lush, Dinosaur Jr., and Slowdive. The Mary Chain were controversial from the start, with their sexually suggestive lyrics, limited technical ability, and notorious 20-minute live gigs. But for all the shock value, brothers William and Jim Reid wrote damn catchy songs with simple, classic melodies, albeit buried amid of peals of wiry guitars and a primitive wall-of-sound production. They cribbed liberally from their forebears -- VU, the Beach Boys, Phil Spector, the Ramones -- arriving at a formula that they would refine over their decade and a half together. Arranged chronologically, 21 Singles traces their fits and starts, from the raw, untempered aggression of the early singles -- "Upside Down," "Never Understand," "You Trip Me Up" -- through periods of sparse tunefulness ("Just like Honey," "Darklands"), catchy, radio-friendly melodies ("April Skies," "Far Gone and Out"), and more densely layered aggression ("Sidewalking," "Reverence"). It also marks their lone entry into the U.S. pop charts via the chiming single "Sometimes Always," a sweet duet with Mazzy Star's Hope Sandoval. An essential document of one of alt-rock's most influential bands, 21 Singles winds down with "I Hate Rock n Roll" and "I Love Rock n Roll," both from their 1998 swan song, Munki. It's a keen summation of a band that took a few loud chords, a giant ego, and loads of creative juice as high -- and as low -- as they could go.