As the sole full-length snapshot of the band's Syd Barrett era, The Piper at the Gates of Dawn neatly sums up what made their first incarnation great-- the balance of whimsy and discomfort, displayed in the band's ability to feel at home inhabiting both chart-friendly psych-pop ("Arnold Layne"; "See Emily Play") and experimental space-rock sprawl ("Astronomy Domine"; "Interstellar Overdrive"). The remainder of the records from the 1960s and their first album of the 70s-- A Saucerful of Secrets, Music from the Film 'More', Ummagumma, and Atom Heart Mother-- reveal a band in continuous and restless transition, looking for their footing and a new identity after Barrett's departure. These records are Pink Floyd at their most aimless-- for every indelible moment like the slow creep towards screaming violence in Ummagumma's live version of "Careful With That Axe, Eugene" or their bid for Beach Boys teenage-symphony pop in Atom Heart Mother's "Summer '68", there's the tedious multi-part suites that toy with experimentalism for its own sake, some good-start-no-finish soundtrack tidbits and that one Ummagumma track where Roger Waters made a bunch of silly animal and/or ranting Scotsman noises and slapped a big unwieldy 16-word title on it.

And then there's the blockbuster stuff. With the exception of 1972's soundtrack-fodder footnote Obscured By Clouds, everything here from 1971's Meddle through 1979's The Wall has become so ingrained in the rock consciousness, so frequently dissected and joked about and lumped in with the Eagles and Yes in the textbook entry for Reasons Punk Had to Happen, that it's easy to forget why Pink Floyd got so huge in the 70s. (I'll pause to let you construct your own pot joke.) That they released some of the most slickly-produced and stylistically versatile music of its time-- simultaneously playing to the strengths of psychedelia, prog, and even r&b (ever play "Echoes" and Isaac Hayes' "Walk on By" back-to-back?)-- probably didn't hurt their commercial prospects, but a significant portion of their work, The Dark Side of the Moon in particular, was wrapped up in Waters' obsessive search for some kind of human empathy, and in the midst of a culture filled with rampant post-hippie ego-tripping and waning optimism that search rang true with a number of adolescents and college students-- and not just the ones of the 70s. Things do get shakier the further we get into the 80s and 90s: The Final Cut is draining if occasionally patience-rewarding, but the David Gilmour-fronted records A Momentary Lapse of Reason and The Division Bell are cruise-control adult-contempo dross that sand off every edge the band had.