Spirit were one of the most original groups of psychedelic rock, although their style was never as spectacular or cacophonous as that of the majority. Every one of their songs was a triumph of tasteful little experiments. They were perhaps the inventors of progressive rock, a couple of years before the British turned it into a fashionable phenomenon.

Spirit were born in 1967 from the partnership between a very young rock guitarist (Randy California, born Randy Wolfe, an emulator of Jimi Hendrix, already leader of a garage band) and an elderly jazz drummer (Ed Cassidy, a veteran of jazz musicians such as Thelonious Monk, Art Pepper, Cannonball Adderley and Gerry Mulligan, and previously with the Rising Sons of Taj Mahal and Ry Cooder in 1965). They were joined by other veterans of the Los Angeles scene: bassist Mark Andes, guitarist Jay Ferguson and keyboardist John Locke.

Their first single, Mechanical World, was already an unusual song, but it was the debut album, Spirit (Ode, 1968), that truly did justice to their eclecticism. The tracks shifted effortlessly from one style to another, elegantly and skillfully experimenting with the most cerebral combinations. Their psychedelic phase was represented by Fresh Garbage, acidic and polyrhythmic, jazzy and distorted, and by Taurus, California's masterpiece (with flute, violin and harpsichord), pieces that seem to wander in the void and for precisely that reason rank among the most unusual experiments of psychedelic rock, anticipations of progressive rock. California invented a guitar language that was certainly descended from Hendrix, but that integrated “effects” more organically into the group sound.

The group's ambitions culminated in The Family That Plays Together (Ode, 1968), the album that ranges from the driving, almost hard-rock riff of I've Got A Line On You (their biggest hit) to the melodic fantasy of Silky Sam - Drunkard - Dream Within A Dream. The first side is in effect an elaborate multi-movement suite. The counterpoint between the instruments had reached an almost transcendental level of sophistication. References to blues, jazz, raga and rock dissolved into a kaleidoscope of soft timbres.

Clear Spirit (1969) is a more banal hard-rock album (Dark-Eyed Woman, 1984), with the only consolations being the sophisticated score of Ice and the dreamlike Clear.

Twelve Dreams Of Dr Sardonicous (Epic, 1971) was their most baroque album, arranged with synthesizers (Space Child, Love Has Found A Way) and studio effects. It showcases the frenzied country-boogie of Animal Zoo, the eccentric lysergic pastiche of Nature's Way, a roaring, Hendrixian and epileptic Nothing To Hide, the grotesque funk of Mr Skin, and the surreal acoustic interlude Why Can't I Be Free.

Ferguson later formed Jo Jo Gunne, a mediocre hard-rock group. Spirit still released Feedback (1971).

California, having recovered from a nervous breakdown, later recorded the solo album Kaptain Kopter (Epic, 1972).

The reunion album Spirit Of '76 (Mercury, 1975), a double science-fiction concept, seemed promising (even if the best tracks were perhaps the covers), but its continuation, Son Of Spirit, was not very honorable. Future Games (1977), on the other hand, was a return to the more experimental format, a collage of noises, voices and songs.

Time Circle (Epic, 1991) is an excellent anthology.

Randy “California” Wolfe drowned in 1997. The double-disc Sea Dream (Acadia, 2002) and the double-disc Blues From the Soul (Acadia, 2004) collect unreleased material.

Ed Cassidy died in 2012 at the age of 89.