Thanks largely to the funky charms of “Roundabout,” Fragile is the album that came to define the Yes sound. Their rhythmically pugnacious progressive rock is a patchwork quilt of musical fragments, some of which are entire songs (“We Have Heaven,” “Cans and Brahms”), while others are woven together into longer tracks. “South Side of the Sky” and “Heart of the Sunrise” benefit particularly from this approach, making sterling use of Rick Wakeman’s synth cascades against Chris Squire’s forbidding bass attack.