SUB POP CASSETTES Sub Pop continues to innovate in the field of recorded music by releasing acclaimed works by Nirvana, The Postal Service, and Sleater-Kinney on the exciting cassette-tape format. Each cassette features two full sides of music, wrapped in a four-panel sleeve and a sturdy, plastic case, giving you the key features of the popular vinyl, compact disc, and digital albums, but in a unique format that users are calling "physical," "nifty," and "compatible with the sound system of a 1987 Toyota Corolla."