If the founding of Scottish Opera in Glasgow in 1962 formed the great turning point in Scottish music in the second half of the 20th century, the Scottish premiere of Britten's War Requiem in Edinburgh two years later was likewise a triumph of far-reaching importance.

The work – a masterpiece by a great pacifist composer on the theme of "war and the pity of war" – had been unveiled, to huge public acclaim and a dash of critical hostility, in the reconstructed Coventry Cathedral on May 30, 1962, two decades after the original building was destroyed in a devastating German air raid. Many big names, including Sir Basil Spence as architect, Graham Sutherland and John Piper as artists, along with Britten himself, had contributed to the undertaking.

On the same night in another part of Coventry, Scotland's Oscar-winning cinematic documentary, Seaward the Great Ships, based on a screenplay by the irascible John Grierson, happened to be receiving a special showing. As a roving critic, I had hoped to review the requiem, but the film was what my Scottish newspaper – not at that time The Herald – insisted I saw. Thus I missed what should have been one of the most important events of my career. Britten, to my chagrin, had to wait. More performances were in the offing, though none of them as yet in Scotland where vital new music could traditionally take many years to arrive.

Had the Scottish National Orchestra been still in the hands of the retrogressive Karl Rankl or Hans Swarowsky, its two Austrian maestri of the 1950s, this was exactly what would have happened. But by 1959 the young Alexander Gibson, with a flair for fresh things, had returned from London to his homeland as Swarowsky's successor, promptly changing the entire musical climate.

Apart from the creation of Scottish Opera, one of his first acts was to preside over the British premiere of Gruppen, Stockhausen's vanguard study in rhythm, tempo and vibration, requiring the services of three orchestras and conductors, in Glasgow's now defunct St Andrew's Hall directly after its German debut. Gibson had his ear on the international pulse. The performance attracted the London critics. Something had suddenly happened in Scotland and it went on happening in Gibson's championing of the music of Hans Werner Henze, in his prolonged Mahler cycle at a time when the symphonies were not yet an everyday event, and in the espousal of more recent composers in his Musica Nova festival, featuring new works by Harrison Birtwistle, Peter Maxwell Davies, Gyorgy Ligeti, Luciano Berio and many others.

The Scottish premiere of the War Requiem proved a pioneering ingredient of all this. Of what the SNO was achieving on behalf of modern composers, the requiem was one of the first and most eloquent manifestations. Yet the prospect of the performance, in the wake of Coventry's, prompted trepidation. At a time when the players were still feeling their way into new music, would the work's intricacies – demanding a big orchestra, a chamber group with a second conductor, two choirs, a tiny but clearly audible chamber organ, and a startling infiltration of the words of the old Latin Mass by the poetry of Wilfred Owen – be successfully resolved?

The Coventry performance, in which Britten had served as second conductor, had worked well. But as soon as the sound of the introductory tolling bells began to mingle with the voices of Arthur Oldham's boy choristers from St Mary's Roman Catholic Cathedral, perched (with the chamber organ) in a corner of the Usher Hall's upper circle, we knew that all was well.

Though Britten's three chosen soloists – Galina Vishnevskaya, Peter Pears and Dietrich Fischer-Dieskau – had been victims of a nasty Soviet veto in Coventry (not until Peter Diamand engaged them for the 1964 Holland Festival would they be heard as a unity) Gibson's substitutes were admirable, with April Cantelo's aching Lacrimosa soaring movingly out of the last notes of the Dies Irae. As the music, on April 10, 1964, delivered its inexorable message, it was destined to remain indelibly in the mind of this novice critic who, having heard it at last, would hear it again in Glasgow the following month, then in Paisley, Aberdeen and further afield.

Indeed, 1964 was a big year for the requiem. My newspaper, having by now bowed to the inevitable, allowed me to review it at the Leeds Festival, with John Pritchard as conductor, and in King's College Chapel, Cambridge, with Sir David Willcocks. And, to cap this, I was dispatched to Holland for the first wholly authentic performance, conducted by Bernard Haitink a month or so later.

These accounts all helped to establish the work in their audience's consciousness. Britten, who had sometimes seemed an over-clever composer, suddenly became a great one, with a cycle of innovative Scottish Opera productions at a time when he was being downplayed in England. In 1968, Carlo Maria Giulini mustered Britten's three desired soloists for a justly famous Edinburgh Festival performance. Gibson conducted its South American premiere at the Teatro Colon, Buenos Aires, before doing it in the Herod Atticus amphitheatre on the slopes of the Acropolis, and then in East Berlin.

The music made its political point wherever it went. Today a new generation of conductors is championing it. By 1991, not long before his death, Gibson himself delivered a searing Edinburgh Festival performance. In 2010, Stephane Deneve did it with the RSNO. Peter Oundjian, Deneve's Canadian successor, is said to be interested in it. Continuity, it seems, is being maintained.

A 50th anniversary performance of the War Requiem by the City of Birmingham Symphony Orchestra and Andris Nelsons will be broadcast from Coventry Cathedral 7.30pm, tonight, on BBC Radio 3.