Brewer, BBCSO, Bělohlávek, Barbican Hall

Exactly an hour and a half after Wagner's first orchestral brew of sex and religion had raised the curtain on the Royal Opera Tannhäuser, the pilgrims and floozies were at it again over the other side of town. If there was hardly the whiff of elemental theatrics ahead in Jiří Bělohlávek's surprisingly staid conducting of the overture, different treats were in store: the most opulent and musicianly of all living sopranos, Christine Brewer, in cheerful love songs by a nearly forgotten Austrian composer, and a smells-and-bells pilgrimage up a mountain and down ennobling Richard Strauss's most natural orchestral work.

If you haven't heard anything by Joseph Marx, a natural heir to Strauss a notch above Korngold, then you can't do much better than listen to the Chandos disc including the orchestrated versions of some of his hundred-plus songs (pictured below). Except, of course, hear the same artists, Brewer and Bělohlávek, in the flesh. For the great lyric-dramatic soprano's opulent tone is one of those sounds recording can't do justice. Bělohlávek knew he didn't have to rein in a muscly-sensuous BBC Symphony Orchestra; it was right to let the voice rise and fall on those gorgeous tides. We've heard some so-so orchestral songs at the Barbican of late, and while the Marx numbers might not have been in the very front rank of Mahler and Strauss, their un-angsty paeans to love were a wholesome antidote to rather more sicklied-o'er decadence.

The artists were right to bookend a modest, if dancing group of six with two fuller-hearted rhapsodies. "Barkarole" is a sparkling marine picture, the orchestra adding ever-richer frolics of its own between stanzas and splashing the singer's far from frail bark with water music almost as wonderful as the cataracts to come in Strauss's Alpine Symphony. And when the ecstatically received team reprised the last song, "Hat dich die Lieber berührt", we hardly recognised its new intimacy after the extrovert way it had just been presented, with Brewer pulling out all the stops for the big final phrases.

Inspirations in between were too short and to the point to merit the splattering of applause between each. It's worth comparing Marx's to-the-point setting of "Waldseligkeit" with Strauss's more leisurely reverie. I love them both, but what made Marx's orchestration special was the string homage to the final transfiguration of Schoenberg's Verklärte Nacht. Since that's based on a reconciliatory poem by the same author, Richard Dehmel, I'm assuming the sound world was more than a coincidence. All these simpler numbers were enriched by Brewer's palette of tone colours - the selectively cavernous middle range, the secure lower register - and by her easy motion on the crest of the orchestral wave.

That the orchestra is on peak form under Bělohlávek could never be doubted in the firmly shaped but leisurely trajectory of Strauss's 24 hours in the mountains. Perhaps the "mountaineers" - strictly, walkers - who appear in all that splendour could have made a more rugged, less pious ascent, but who could blame them for gaping and worshipping all that beauty. Direct if unsensuous strings, keen-cutting clarinets and firm tuba bass lines kept the outpourings from turning to mush, and it was a wonder to watch the usually reserved Bělohlávek pulling out all the supple conducting stops on the summit: fascinating to compare with Andris Nelsons' wild but clearly inspirational flappings in the Birmingham performance I heard earlier this year, and eliciting equally climactic results.

Most of the high jinks came off, as did the metal thunder-sheet from its moorings once the percussionist had shaken the hell out of it at the two-and-a-bit bars of storm-peak (who could blame him for having a good laugh?). The disquiet that opens, closes and shadows the brighter side of nature was also as compellingly done as Barbican acoustics allow. I took the nine-year-old son of a friend who was riveted from start to finish, and asked him whether it all conjured up anything besides the descriptive titles we followed so closely. His answer? "I think life and death - the opening is a bit like before you're born, and the end is a funeral." Strange, perceptive child. As for me, I could wish I was back in my teens discovering the wonders of the Alpine Symphony's vast landscape for the first time. Certainly it was marvellous to see the students peppered around the hall rising without a moment's hesitation to their feet at the end of this hallucinogenic trip.

• Find Christine Brewer's recordings on Amazon
• Listen to the Radio 3 broadcast of this concert on Monday 13 December and for the next seven days on the BBC iPlayer
• See what's on at the Barbican this season.