This concert was worth attending just to hear mezzo-soprano Sarah Connolly sing the last “ewig” (forever) in Mahler’s Song of the Earth. She modulated it so that it seemed to rise from, then sink into, an eternal vanishing point. Overcome, conductor Yannick Nézet-Séguin needed several moments before he could cue the uproarious applause. Mahler was chiefly responsible for the hall paralysed with emotion. For an hour he dangles us on the edge of the abyss, then, just as we are about to be engulfed by misery, floats us on a mist of hope. Ms Connolly must however, share the blame. She was simply magnificent, easily equalling the most illustrious past interpreters of this work.

Counterbalancing Mahler’s contemplation of the transience of life, the first half of the evening comprised Beethoven’s “Pastoral” Symphony, a city dweller's vision of the restorative and exhilarating powers of nature – a fascinating twinning, not just because nature links the two thematically, but because mood-wise they are each other's colour negative. Beethoven’s natural world is benign, optimistically reproducing itself to the sound of carefree birdsong. A century later, Mahler’s natural canvas is mysterious, its preternatural birdcalls evoking death. Its beauty confronts human beings with their mortality and steeps them in despair.

There is no Adagio movement in Beethoven's Sixth Symphony – the initial excitement at reaching the bucolic destination is sustained throughout. Mr Nézet-Séguin tenderly contoured the short motifs in the first movement, repeated and varied in a kind of proto-minimalism, stringing them together into delicate garlands. In the second movement, the "Scene by the brook", he made the water glide rather than burble over the polished stones. The sounds he coaxed from the Rotterdam Philharmonic were perhaps too smooth for this springy jaunt, but undeniably enchanting: string tremolos like quivering spider's threads, honeyed hunting horns, woodwinds chirping in the sweetest of tempers. During the affectionate parodying of the village band in the scherzo, he left the dignity of the amateur musicians intact. His country dancers may have been flushed with cider, but they were as poised as courtiers. He tautly controlled the storm that breaks up their merriment, flinging out the full force of its stun-gun rhythm. In the final movement, the idyllic softness gained more definition, with the teeming motifs jostling each other towards the climaxes and a lambent prayer-like moment of gratefulness.

A singer's concert garb is immaterial, but Ms Connolly’s black gown, trailed with sprays of white appliqué flowers, had an Aubrey Beardsley feel that transported us to the right era for the Mahler. In 1908, a year after his eldest daughter died of scarlet fever and he himself was diagnosed with a congenital heart defect, Mahler began setting translations of ancient Chinese poetry. "All of his sorrow, his fear, he put into this work," his wife Alma wrote. In the crucible of his grief he forged a new musical form, the song-symphony. Six songs, all different in atmosphere, are musically linked by major-minor tonality and a strong pentatonic flavour. The poems explore the illusory essence of life and the futility of trying to escape sorrow, but Mahler adapted them to encompass his belief in the afterlife, possibly by becoming one with eternal nature. Despite the huge orchestra, the score often deploys instruments a few at a time, which showcased fabulous soloists such as Juliëtte Hurel on the flute and first clarinet Julien Hervé, but also marvellous bassoon, oboe, violin and cello solos. 

Although not completely flawless in execution, Mr Nézet-Séguin and his musicians delved deep into the mystery of the work, unfurling it with persistent phosphorescence that periodically flared into dramatic starbursts. They were also consistently in touch with the singers. Tenor Robert Dean Smith met the onerous demands of the first song head-on, vaulting over the orchestra to conjure up the horrific simian apparition howling in the graveyard. The jolt with which he launched his top notes and their brightness suited the breaking-point desperation of the two drinking songs, and he also found a swinging lyricism for the whimsical "Von der Jugend" (Of Youth). The power of Sarah Connolly's interpretation was rooted in her complete engagement with the words. Whether in the plunging melancholy of "Der Einsame im Herbst" (The Lonely One in Autumn) or when limpidly describing young women gathering lotus flowers in “Von der Schönheit" ("Of Beauty"), her voice emanated a soft but penetrating radiance. The breadth in the contralto range and the tonal integrity across all registers make hers a truly exceptional instrument. Besides being unutterably moving, her final song, “Der Abschied” (The Farewell) had a sweeping vocal majesty. It advanced, as it should, like a slow-motion tremor tearing the loamy earth to reveal wounds in intense orchestral reds and purples, before melting into those wondrously sung "forevers".