{TABLE} Imprompus D899 ................ Schubert Suite Op 25 .................... Schoenberg Sonata in B flat D960 .......... Scbubert {/TABLE} Impromptu, the music dictionaries tell us, is not a designation meant to suggest an improvisatory style of composition but rather the casual, or impromptu, nature of the musical inspiration. And the sense of spur of the moment was paramount in Mitsuko Uchida's playing of Schubert's first set of impromptus at the NCH/The Irish Times celebrity concert on Saturday.

From the first declamatory note, a considerable sense of tension was generated from the feeling that options were being kept open as long as possible until the crucial decision to pounce or caress was reached. Uchida's was an approach which courted extremes, bringing her at times to dig for rather more than either the music or the NCH's Steinway seemed to have ready to yield.

To my ears, her softer manner came closer to the heart of the music than her heightened ventures into stormy, even tortured, expressiveness.

Schubert's final B flat Sonata is one of his most remarkable creations and Uchida responded rewardingly to its every challenge. Most notable was the slow movement, its mood of unutterable resignation unerringly gauged, with the top notes of the left hand's rising octaves touched in as though by a scarcely audible breath. The fluid rippling of the Scherzo, the delicate dance of the finale and the hushed expansiveness of the first movement were scarcely less impressive.

In the central work of the evening, Schoenberg's Suite Op. 25, Uchida flashed and sparkled and growled. This piece, written in the early 1920s as a sequence of classical movements in the then new 12 tone technique, still represents a knotty aesthetic undertaking for performers its density is obvious and, therefore, its (to many people unexpected) lightness and wit are altogether too easy to forego.

Without essaying either the fantasy of Glenn Gould or the rigour of Maurizio Pollini (to look to two of Schoenberg's staunchest advocates), Uchida played with a brio and passion that brought cheers among the applause at the piece's close.