As the '50s gave way to the ’60s, the cross-pollination of rock, pop, and R&B blossomed into a wave of outwardly cheery but emotionally layered girl groups who mastered a resilient wall of group vocals. Harmonizing through relatable tales of teen turmoil, young ensembles like The Shirelles and The Shangri-Las explored dark, sometimes sensual melodrama within the safe confines of snappy sing-alongs. That said, savvy writer/producers like Phil Spector seized on the marketability of this fresh sound to push out the boundaries of pop arrangements, sweeping humble handclaps and castanets into dense mini-symphonies. Though the sound enjoyed peak success for only a handful of years before the British Invasion, it yielded songs as primitive as The Dixie Cups’ “Iko Iko”—on which a schoolyard-style chant is accompanied by percussion performed on ashtrays and soft-drink bottles—and as polished as The Supremes’ “Baby Love,” a romantic lament couched in the upbeat trappings of lush, widescreen orchestration.