First released in 1971, Who's Next towered -musically, technologically and conceptually - over its close rivals that year, Led Zeppelin IV and the Stones' Sticky Fingers. It emerged from the wreckage of Lifehouse, Pete Townshend's ambitious proposal for a movie and concept album, begun hot on the high-stacked heels of his hugely successful rock opera Tommy. In precis, Lifehouse was to be a journey through the scarred wasteland of a futuristic middle England, where a computerised 'Big Brother' grid imposes virtual reality on the populace and the subversions of rock music offer the only salvation. Heady stuff.

Townshend's compositions for Lifehouse were unveiled at a Who concert staged specifically for the event at London's Young Vic theatre in April 1971. But within months the project ran out of steam: it was too unwieldy and the songs gathered offered the listener no discernable narrative. An over-cerebral plot line belied the stunning immediacy of the music. The film shelved, studio sessions of the soundtrack without a movie were undertaken in New York and London, and it is these recordings that were eventually slated for Who's Next. Originally planned as a double album, the running order was later whittled down to nine songs and a single album was issued in autumn 1971. Three tunes also intended for Lifehouse, but somehow lost in the shuffle when Who's Next was track-listed, appeared on seven-inch only ''Let's See Action'', Join Together and Relay.

And now, over 30 years on, Whos Next still rattles the speaker cabinets. The production (by the band with assistance from Glyn Johns) would hardly shame a four-piece rock band today. It really was sonically far ahead of its time. Through "Bargain", ''The Song is Over'' and ''Behind Blue Eyes'' Roger Daltrey sings with passion and power. His blood-curdling scream at the end of the epiphanic ''Won't Get Fooled Again'' is one of the defining moments in rock'n' roll. Bass player John Entwistle plonks exquisitely throughout, especially on ''Getting in Tune''. Keith Moon keeps the beat like an octopus on uppers.

But this is very much Townshend's album. On the opening track, ''Baba O'Riley'', the cyclic, synthesised introduction becomes the springboard for one of his trademark riffs. In fact the album was the first within blues-based rock to properly employ the synthesiser. On tracks such as ''Going Mobile'' Townshend puts it to work as an instrument in its own right, rather than a device for novelty bleeps.

The original album now benefits from bonus tracks like the melodic "Pure And Easy". Sadly, the three contemporaneous singles mentioned above, very much a part of the albums history, are not included, but instead we have a fascinating, previously unreleased, 73-minute CD of the Young Vic concert, when much of this material was first aired. The expanded Who's Next keeps its place as one of the essential, most exciting rock albums of the last forty years: now bigger and better than ever. Meet the new boss...