There are times - not many - when a concert goes beyond being just a concert and transcends itself, performers and audience together entering an entirely different state of engagement. Not merely profound (although it is profound), but other. This is what happened last night in Gloucester Cathedral, at the Three Choirs Festival performance of Berlioz’s Grande messe des morts.

The occasion was more than usually solemn. With recent terrorist atrocities in France uppermost in everyone’s minds, this grand memorial for the dead (originally commissioned to commemorate the fallen of the 1830 French Revolution) took on a particularly painful poignancy. It was impossible not to see gaping ideological contrasts. The figure of Berlioz: progressive, radical, seeking ever new ways to encapsulate emotional truth, unafraid to jettison or invent anything along the way irrespective of tradition or sentiment; and his Requiem: unflinchingly forward-looking, a seamless synthesis of religious belief and human feeling, courageously sweeping aside conventions of orchestration and word-setting and in the process giving birth to Romanticism, to Expressionism, and even pointing the way to Modernism and experimental music. Contrast that with the backward, narrow outlook and cowardly violence to which France (in particular) has recently been subjected, and perhaps there has never been a more appropriate, a more urgent time for Berlioz’s Requiem to be heard.

Enter Edward Gardner, marshalling the vast combined forces of the Three Choirs Festival Chorus and the Philharmonia Orchestra, augmented with four satellite brass groups and the inclusion of a huge battery of timpani. Conducting Berlioz’s Requiem is a feat, and Gardner gave the tour de force performance of his life. His tempi never dragged, never sought even for a moment to milk the exquisitely piquant melodies, the mournful introspection, the music’s desperate gazing into the infinite and hoping against hope that the words aren’t being uttered in vain. Thus, the Kyrie became a fittingly subdued, almost mumbled series of abject apologies, while the Dies Irae, in which Berlioz continually ratchets up the tension, was pushed by Gardner harder and harder as though moving up through a series of gears. And when the inferno came, in the Tuba Mirum, Gloucester Cathedral became incandescent, radiating with a terrifying intensity of light and warmth as every performer on stage, as one, unleashed fire. Scarcely credible in this onslaught was the clarity, the orchestral balance clean, every instrument audible, the choir immense but never overpowering, in which even the timpani chords could be heard as chords. Surely the Last Judgement has never resounded with such vivid detail and colouration. The same was true through the almost operatic dramatic contortions of the Rex Tremendæ and the paradoxically lilting but furiously unstoppable momentum of the Lacrymosa; the latter was especially impressive, never shrill, never overblown, yet nonetheless threatening to reduce the cathedral to ruins with its raw power.

Berlioz structures the Requiem such that these huge pinnacles of overload are immediately followed by gentle episodes of quiet contemplation, and these proved revelatory. Quid sum miser miniaturised everything to the size and scope of chamber music, whereas in Quærens me – a delicate slice of unaccompanied choral counterpoint reminding us all that, despite appearances, this is first and foremost church music – the orchestra vanished, shining a spotlight on the chorus who reached a high point of soft sublimity. For the Hostias, the Requiem’s most weirdly left field movement, Gardner went further, teasing out a wonderfully unsettling sense of underlying aggression and dread, casting ominous shadows over the choir’s supplications.

The Offertorium and Sanctus are among the most beautiful music Berlioz ever composed, and the former was profoundly moving, Gardner allowing the choir to remain seated to enunciate their repeated, simple two-note oscillations as the Philharmonia canonically tilt-shifted the harmony around them. The latter, featuring tenor Robert Murray high up in the organ loft, was almost too much to take. Murray’s nicely-measured delivery (which felt both personal and intimate) was mirrored by the choir, before letting rip in the lengthy pair of Hosanna fugues. Gardner united everyone on stage for the heavyweight octave unisons at their conclusion, turning the Requiem’s final fortissimo into a blaze of tearful triumph. This tone persisted through the work’s peroration, one of the most exhausted settings of the Agnus Dei ever written, where Gardner injected new life into the reprised passages from earlier. Whereupon choir and orchestra (including the timpani, mollified at the last), quietly entered into peace.

This was nothing less than a landmark performance of a landmark work. 179 years after its première, Berlioz’s Requiem continues to reveal and remind, in its determination to be creatively radical, in its honest, wounded faith, and above all in its central acknowledgement that while death is always terrible, hope remains eternal.