RARE INDEED are those occasions when a concert enshrines a performance that is so special that you savour the privilege of witnessing it. Such was the effect on Tuesday night when the American mezzo-soprano Michelle DeYoung, the Philharmonia and Pierre Boulez held the audience on the edge of a shared breath for the last of Mahler's five Ruckert lieder.

"I live alone in my heaven, in my loving, in my song", writes the poet, and when DeYoung had sung her final lied, Boulez and his players (the strings in particular) responded with a degree of rapt tenderness that was unique in my experience. In a truly great performance, every phrase, every textural component fitted its context without any slack. Tempos were perfectly judged, yet each orchestral soloist enjoyed what seemed like infinite breathing space. It was an inspiring example of interpretative rightness.

The concert was the latest instalment in the Philharmonia's ongoing series "Mahler & Vienna - Beginnings & Endings" and Mahler's song-cycle was its undoubted highlight. DeYoung's contribution to the first half was for Schoenberg's "Song of the Wood Dove", a sombre elegy taken from the epic Gurrelieder and pared down from a large orchestra to just 17 players. No one could have faulted Boulez, the Ensemble Intercontemporain or DeYoung's effulgent singing. Yet when taken out of context, Schoenberg's dank, post- Wagnerian essay seems excessively indebted to a musical language that even by 1911 (the year Gurrelieder was completed) was already suffering its death throes.

The concert opened with Boulez and the Ensemble in Schoenberg's restless First Chamber Symphony, a workwhere the pull between post-Romanticism and Modernist innovation makes for some fascinating tensions. Themes crowd past in heady profusion and the sum effect is anxious, overwrought and compulsively busy.

Placed next to it, Anton Webern's four-minute Five Orchestral Pieces becomes a select community of exquisite tropical birds. Webern's orchestration incorporates sundry colourful instruments, all used with the greatest economy. The pulsing third piece is gentle yet starry-bright, suggesting vistas way beyond its miniaturist length.

The concert ended with what is perhaps the cornerstone of 12-tone music, Schoenberg's masterful Variations for Orchestra, Op 31. Some of the audience walked out after 10 minutes, others stayed to cheer the Philharmonia's performance. The Variations end with a bang, but on leaving the hall, all I heard were rave reactions to Mahler, DeYoung, Boulez and Ruckert's solitary loving. Innovative compositional systems are all well and good, but taking music to heart is quite another matter.