Pink Floyd is the premier space rock band. Since the mid-'60s, their music relentlessly tinkered with electronics and all manner of special effects to push pop formats to their outer limits. At the same time they wrestled with lyrical themes and concepts of such massive scale that their music has taken on almost classical, operatic quality in both sound and words. Despite their astral image, the group was brought down to earth in the '80s by decidedly mundane power struggles over leadership and, ultimately, ownership of the band's very name. After that time, they were little more than a dinosaur act, capable of filling stadiums and topping the charts, but offering little more than a spectacular re-creation of their most successful formulas. Their latter-day staleness cannot disguise the fact that, for the first decade or so of their existence, they were one of the most innovative groups around, in concert and (especially) in the studio.