In a castle in mediaeval Denmark, King Waldemar and Tove sing rapturously of their love. But dark deeds are afoot: a Wood Dove tells us that Tove has been murdered by Waldemar's jealous queen, Waldemar berates God, he and his men are condemned to rise from their graves every night and ride in a wild hunt - all this to the accompaniment of a giant, brass-laden orchestra playing a lush, opulent symphonic score filled with repeated and transformed motifs.

You'd be forgiven for assuming that I'm talking about a Wagner opera, but in fact, this is Schoenberg's massive secular cantata Gurrelieder, begun in 1900 (when Schoenberg was 26), set aside several times and eventually premièred in 1913. For those who associate Schoenberg with dodecaphonic composition and harsh atonality, the score is an eye opener: it has the high romantic symphonicism of Wagner and the breadth and magnificence of Richard Strauss. In the work's later stages, some distinctly Mahler-like dances, marches and touches of nature leak into the overall musical narrative.

Jens Peter Jacobsen's poetry (originally written in Danish but translated into German for this work) is blissfully evocative, and in many places, the music packs gigantic punch, comparable to the opening of that other great secular cantata Carmina Burana. To help produce this impact, Schoenberg demanded massive forces (extraordinarily so for a composer of his age) - no less than 25 brass players, 26 woodwind, 4 harps, a narrator and five singers. The second half demands three four-part male choruses, augmented by a mixed choir for the final chorus - around 400 musicians in all.

The sheer amount of sound that the BBC Symphony Orchestra produced was thrilling, but therein lay the biggest problem of this Prom: much of the time, the orchestra completely overwhelmed the soloists. Simon O'Neill, as King Waldemar, has a smooth, lyrical voice that is lovely to listen to, but the score of Gurrelieder requires him to tower above the orchestra at dramatic moments. On the night, most of these high impact moments were lost, and in some of his quicker passages, O'Neill was totally inaudible. As Tove, Angela Denoke fared better: she has gentler music to contend with and the clarity and smooth timbre of her voice was mostly able to cut through the orchestral wash. Denoke has had a mixed press this year, and while this may not be the most virtuosic of soprano parts, I still thought it was a performance to confound her critics. The Wood Dove gets one long aria which is the emotional centrepiece of the work, Katarina Karnéus sang it quite beautifully, although her most critical moment - the announcement that Tove is dead - lacked the shock effect of which the music is capable.

More generally, the orchestral performance was patchy. The BBC Symphony, under the baton of Jukka-Pekka Saraste were at their best in the fast passages which prefigure 20th century film music and in the large tutti, genuinely able to lift you out of your seat. But this is a work that demands high accuracy of timing, and the timing often wasn't quite sharp enough in the many little orchestral asides from groups of more than one instrument (these are especially present in the latter half of the piece, (by which time Schoenberg had been absorbing some of Mahler's techniques). Entries which should have been together were just slightly ragged, enough to break up the overall effect of this complex composition.

The richness of the love music alone in Gurrelieder makes it a masterpiece, and each number has its own beauty and excitement, although the integrity of the work suffers somewhat from having been written over a period of thirteen years, during which time Schoenberg's view of himself and his music changed completely, and he had fallen out of love with Gurrelieder to the point where he was rather upset when its première proved a great success with the critics. Yet in this Prom, it was the most idiosyncratic of the numbers that came through most strongly: The Wild Hunt of the Summer Wind is an obscure, allusive poem performed in sprechgesang style - the words spoken but with a musical lilt - that Schoenberg would later make famous in Pierrot Lunaire. Wolfgang Schöne gave us lovely timbre and phrasing, his pitch rising and falling to follow the swell of the music and the elegiac lilt of Jens Peter Jacobsen's poetry.

Gurrelieder is a magnificent work: I'm thrilled to have seen it and I'll be taking any opportunities I get to see it in future. But I suspect that it might be easier to perform in an opera house than in a concert hall, where the singers get no protection from a big orchestral sound coming from behind them. It's particularly problematic in a hall the size of the Royal Albert Hall, and Saraste failed to overcome the inherent difficulty of performing this work in this venue. The result was a performance that retained some of the work's magic but left me wanting more.