Classical: Kurtag at 70 SBC, London

'His works solve the puzzle of 20th-century language by saying everything they need in less than 10 minutes'

Size isn't everything, and in the case of the London Sinfonietta's South Bank celebration of Gyorgy Kurtag's 70th birthday, the Hungarian composer's brevity of thought was a real advantage: "soundbites" in a virtuous sense of the word, with a pun that implies both artistic taste and verity, his works solve the puzzle of 20th-century language by saying everything they need in less than 10 minutes.

Webern did much the same, of course, but in his utter purity denied himself the plethora of historical reference heard, for example, in the selection of Kurtag's piano-duet Jatekok ("Games") and Bach transcriptions on Friday evening in the Purcell Room. Following on from the early Sayings of Peter Bornemisza, and with the Messages of the Late Miss RV Troussova sung by Rosemary Hardy in the QEH on Saturday, they offered a touchstone - domestic rather than scenic - of Kurtag's musical manners. New works filled up the remainder of the programmes. The result, thanks to the composer's slender output, was a rounded picture of his mature style.

Standing in at short notice for Kurtag and his wife, Valeria Szervanszky and Ronald Cavaye brought balance and clarity to the Jatekok duets, sharp- witted heirs to Bartok's Mikrokosmos. Clouds of white-note glissandi made a candy floss "Perpetuum mobile". In "Beating-fighting", the pianists squabbled over who should play three chromatic notes. Kurtag made music from a gesture or the resonance of a single tone, a discipline also central to the second and third string quartets heard later that evening in exemplary accounts by the Keller Quartet. Tersely dramatic mosaics, they contrasted with the sombre impressionism of In memoriam Andras Mihaly, a piano solo "resonated" for keyboard and strings by Thomas Ades, and the dreamlike Lebenslauf, for pairs of pianos and basset horns.

With trumpeter John Wallace and Sinfonietta pianist John Constable, Ades was soloist in Ruckblick: Homage to Stockhausen in Saturday's late-night recital. A London premiere, this hour-long anthology of Kurtag chosen by himself required playing and listening of extreme concentration as it ranged, like the other concerts, over three decades of creative experiment. In this case, the composer's stylistic integrity seemed counter-productive, jading the appetite after so many nourishing morsels already consumed that evening.

Two of these were premieres that gave recent snapshots of the potent miniaturism that remains Kurtag's most compelling artistic quality. Cellist Christopher van Kampen and pianist Csaba Kiraly played the mysterious Double Concerto, conducted by Markus Stenz, a major asset to this orchestra. In Grabstein fur Stephan, a fantasia on the open strings, guitarist Steven Smith went quietly amid the noise and haste of Sinfonietta musicians arranged, as in the concerto, throughout the QEH.

Space has become the latest motif in Kurtag's world of thought and feeling, with intriguing (if so far provisional) results. Four viola pieces played by Paul Silverthorne had the feel of more classic Kurtag: brief yet charged with emotion, and economical, in a virtuous sense, with the truth.