The Prokofiev Seventh Sonata remains a benchmark recording not only for the athleticism of its outer movements but for the epic remorselessness of the central Andante. The Webern Variations are a magical fusion of intellectual passion and poetry, and the Boulez Sonata vividly reminds us why the European avant-garde was such a powerful form in the 1950s.

As astounding a collection of virtuoso piano-playing as when the LP version appeared. Pollini is a complete master of these immensely challenging pieces.

In a few minutes you hear what makes Boulez's music so enticing: the incredibly subtle harmonic sense, whose roots in Debussy and Messiaen become increasingly overt as the years go by; the combination of luxuriant decoration and sudden pouncing violence; and a constantly changing pulse. Like Debussy's, Boulez's music is always 'pushing forward' or 'holding back'. The conductor who best realises this cat-like flexibility is of course Boulez himself. And given his massive authority as a conductor in new music generally, the question "Which version should I buy?" seems to be answered as soon as it's asked . . . Boulez describes the piano as 'an instrument peculiarly prone to frenzy', and the second sonata of 1958 combines an expressive fury with a Beethovenian grandeur and reach. There are now six versions of this piece in the catalogue, but the most craggily impressive is still the one from Maurizio Pollini on DG. Beside the violence, you find in early Boulez a hot sensuality, different to the glittering, rather cool beauty of the later works.