The Ulysses Ensemble started life at the International Musicians' Seminar at Prussia Cove in Cornwall, and made their debut at the Aldeburgh festival two years ago. The group are dedicated to 20th-century music and began this Wigmore Hall appearance with what has become their signature work: Schoenberg's First Chamber Symphony, in the arrangement for flute, clarinet, violin, cello and piano that Anton Webern made in 1923.

It is fascinating to hear such a masterpiece, originally scored for 15 players, from a different perspective. With the piano taking over many of the extra lines and harmonies, the textures are clarified rather than condensed, so that what can seem a rather breathless, overwrought piece seems more lucid and perfectly proportioned than ever. A performance of this standard helps too, with every player absolutely certain of his or her contribution to the total effect.

Webern's arrangement was intended as a companion piece to Schoenberg's Pierrot Lunaire, which uses the same instrumentation, and that is how it was performed here, with soprano Christine Schäfer as reciter. Schäfer is an experienced Pierrot interpreter - she has recorded the work with Boulez - but this performance, more sung than spoken, was surprisingly low-key: neutral to the point of blandness and totally lacking in the nightmarish extremes that make Schoenberg's score one of the highpoints of musical expressionism. Even the vivid contributions of the Ulysses players could not quite fill in for what was missing at its core.

Perhaps Schäfer was suffering from an unannounced ailment, for she was scheduled to sing Ravel's Chansons Madécasses as well, but was replaced by Ailish Tynan. Hers was a beautifully realised performance, languorously seductive in the first song, fiercely protesting in the second, serene in the last, and all perfectly counterpointed by Emily Beynon's exquisite flute playing.