Pink Floyd: David Gilmour (vocals, guitar); Richard Wright (vocals, keyboards); Roger Waters (vocals, bass); Nick Mason (drums).

Disc 1 was recorded live at Mothers, Birmingham, England and live at The

Manchester College Of Commerce, England in June 1969.

Party-liners may favor DARK SIDE OF THE MOON, but diehard space cadets recognize UMMAGUMMA as the pinnacle of post-Barrett Floyd's achievement. Originally released as a double LP, the first record is a live recording from 1969, while the second features four extended cuts written by (and featuring) each of the four band members in turn. Eschewing the catchy, Kinks-influenced pop kaleidoscope of the band's first album, the live portion focuses on extended, spacy near-instrumentals, heavy on acid-fueled jamming and atmospheric electronic textures.

From the Eastern-tinged "Set the Controls for the Heart of the Sun" to the over-the-top psychosis of "Careful With That Axe, Eugene," UMMAGUMMA's first half is ground zero for the genre that would come to be known as space rock. The solo efforts on the second half are undoubtedly the band's most experimental, unconventional efforts ever. They make good use of the avant-garde techniques that were a key early influence, like musique concrete-style tape collage and sound effects. Along the way, there's some lovely folk-tinged balladry, courtesy of Roger Waters ("Grantchester Meadows"), and some proto-prog keyboard wizardry (Richard Wright's multi-part "Sysyphus").