As the driving force behind Pink Floyd in the '70s and early '80s, Roger Waters helmed a series of searching, high-concept albums that reimagined rock as a force of almost symphonic stature, exploring themes of societal alienation (The Wall), class consciousness (Animals), and existence itself (Dark Side of the Moon). Songs like "Comfortably Numb" and "Another Brick in the Wall" braided the band's protestant spirit with science fiction’s dystopic slant. But the Surrey, UK-born singer, songwriter, and bassist didn’t just help expand rock's conceptual vocabulary: Under him, Pink Floyd became one of the first major groups to incorporate synthesizers and sound effects, extending The Beatles’ experiments with tape collage to new technological frontiers. His vision doesn’t end at music. Staunchly anti-establishment, Waters also embodies the figure of artist-as-activist, raising awareness and funds for causes as far-reaching as malaria, climate change, disaster relief, and Palestinian rights. In turn, he has influenced everyone from fellow progressive rock icons Rush to The Flaming Lips and Radiohead—Floyd disciples who turned grand philosophical questions into anthems of substance.