Following the paths blazed by the late Frank Zappa, adventurous musicians continue to redefine the boundaries of what is considered rock music. Inspired equally by modern classical, ethnic and experimental electronic music, groups like Add N to X, Sigur Ros and Mogwai are creating vivid new sounds that defy conventional rock song structures and tonality. Various bands led by Mike Patton (Mr. Bungle, Fantômas, etc.) emphasize off-kilter time changes and virtuosity, while bands like Flaming Lips, Mercury Rev and the Butthole Surfers retain quirky pop appeal while they challenge rock's status quo.