Some advice, dear reader, when listening to Schumann's secular-ish oratorio Das Paradies und die Peri: if you can't cope with Victorian moralistic sentimentality and ersatz orientalism, drop the libretto and just listen to the music. You will be richly rewarded by a cascade of melody, delicious orchestration and beautifully weighted vocal lines, whereas…

Das Paradies und die Peri is one of four tales in Thomas Moore's orientalist romance Lalla Rookh, which was a blockbuster in its day, a couple of centuries ago. It has decidedly not worn its age well: long, verbose and filled with references to obscure Persian places and events while embodying a sentimental Christian message of indiscernible relationship to Persian culture. Emil Flechsig's German is an improvement – considerably shorter, tighter and less cloying – but it remains a difficult text for modern ears.

But Schumann's music is a creation of utter beauty, which can hardly fail to bewitch. And last night at the Barbican, we were certainly treated to a bewitching opening, with Simon Rattle and the LSO's string section producing a tone so warm and shimmering as to transport you from northern winter to sunnier climes faster than a magic carpet. Matching them for warmth was Bernarda Fink, the first of an all-star cast of soloists. Fink's high register was astonishingly sweet, and she gave us a lieder singer's balance and delicacy as well as being able to turn on the emotion by sheer dint of phrasing, accelerating and swelling a phrase to gain excitement, holding back slightly to create pathos.

Mark Padmore joined Fink in using a lieder-like style, singing the Narrator with fire in his eyes and a commitment that would have graced a performance of a Bach Passion. His rich and strong voice contrasted nicely with the clearer and lighter timbre of the other tenor, Andrew Staples.

In the title role of the beautiful fallen spirit seeking a return to Paradise, Sally Matthews started out with a far more dramatic, operatic style which didn't marry up perfectly with that of her fellow soloists. Warm and well weighted in mid range, her voice had a harder edge at the top where the prevailing timbre of both orchestra and other singers was one of sweetness.

Schumann's music is full of surprises. It's not all delicacy and sweetness: the tale of the young warrior destroyed by his tyrannical foe is full of Beethoven-like sturm und drang, punctuated by a high soprano chorus of "weh! weh!" that cuts through the weight of the orchestra in a way that reminds me of passages in Mozart's Requiem. There's a point at the end of Part I (the work is in four parts) where the vocal quartet launches with verve into a classical fugue. There are some imposing choral entries, and hearing the work live from a seat up close to the orchestra brings out some real cleverness that Schumann employs in splitting his string voices.

The highlight of the work, for me, came at the close of part II, just before the interval, where the Peri sings a lullaby (if that's the right word) to the plague-stricken faithful lover, enjoining her to sleep well in eternal rest even as the Peri bears her dying sigh to heaven, hoping that this will be the gift will gain the Peri admission to eternal bliss. The sentiment may be toe-curling, but Schumann's music transforms it into something utterly compelling, and Matthews smoothed out her voice to deliver it beautifully.

The music in Parts III and IV continued to be full of melody and full of contrasts, Rattle's sense of pace and balance continued to display the LSO at their very best, a quartet of young female singers from the Guildhall School generated some genuine excitement and Florian Boesch gave us some cantante passages of very fine quality indeed. But overall, I didn't feel the performance after the interval quite lived up to that before: perhaps the emotional peak had been scaled too soon.

Das Paradies und die Peri is a unique work which sits outside any of the choral categories – oratorio, opera, sacred cantata – of Schumann's day, while the music shows Schumann to have been a more rounded and varied than we often see. There is much rumour and speculation that Rattle's association with the LSO is set to be rather more than just a guest. On the evidence of last night, that's a prospect to savour.