THE Vale of Glamorgan Festival is South Wales's prime showcase for new music. There are few contemporary composers to whom the perceptive artistic director, John Metcalf, a fine composer himself, has not given a platform over the years.

Now, in a tribute originally planned for Sir John Tavener's 70th birthday, but just in advance of the composer's memorial service at Westminster Abbey, it has mounted a retrospective in Tavener's honour.

This festival, under Metcalf's inspired and steadying leadership, casts it net wide. Among countless composers' work reflected, the Australians - Peter Sculthorpe, Ross Edwards, and Gillian Whitehead - perhaps stand out. Metcalf has encompassed music by the South African Kevin Volans, the Americans Hans Abrahamsen and Michael Torke, and Russian-born Elena Langer. Minimalism has its ample say, from composers such as Terry Riley and the late Steve Martland.

The Festival is a pantheon of today's creative talents, both young and old. Jörg Widmann represented German composers this spring; Xiao Ying, now Paris-based, the talent pouring out of China. John Casken, Brian Elias, Philip Cashian, Simon Holt, Huw Watkins, Julian Anderson, Metcalf himself, and Tarik O'Regan (who was specially featured this year, having wonfame for his first opera, Heartof Darkness) are some of thecurrent British figures to be explored.

Formerly centred on the churches and colleges around the Gower Peninsula, south of Swansea, the Festival has, sensibly, shifted from September to May, and, drawing larger audiences, now focuses on Cardiff and its environs, with events spilling over from All Saints', Penarth, to a pier, a castle, and the restored and relocated white Norwegian Church abutting Cardiff Bay.

Undoubted highlights of the week include O'Regan's Acallam na Senórach: An Irish Colloquy, a 20-section work for choir and guitar sung by the Chamber Choir of Ireland under Paul Hillier (founder of the Hilliard Ensemble), who has conducted it for the past six years.

The Tavener celebration formed the peroration of this year's festival. It was to have included Tavener's Celtic Requiem, a work that, with The Whale, established his name as a bold avant-gardist in the late 1960s, and was likewise later recorded on the Beatles' Apple label. That would have been a rare insight into the mind of the younger composer. Alas, owing to a programme change, that was not to be.

But, for this concert, the BBC National Orchestra of Wales was under the baton of the hugely experienced David Atherton, who as founder-conductor of the London Sinfonietta, brought both those works to birth. Instead, we heard Tavener's much later Requiem of 2007, first heard in Liverpool Metropolitan Cathedral, which draws on lines from the Qur'an and Sufi texts - lines as enraptured as the Song of Songs - as well as on the missa pro defunctis.

Equipped with two fine soloists, both scions of the choir of Clare College, Cambridge, nursed to excellence by Peter Dennison, John Rutter, and Timothy Brown, the soprano Elin Manahan Thomas ("I have fallen in love with the Beautiful One who knows no death. . .") and the tenor Nicholas Mulroy ("O Mother, take away my grief, O Thou Essence of Consciousness. . ."), this mighty work welled up miraculously from the depths with double basses, then exploded into a dramaticDies Irae setting and continued highly charged ("Tuba mirum . . . Liber scriptus"), the BBC National Chorus of Wales (chorus master: Adrian Partington) packing a punch throughout.

There is no doubt that the Requiem is one of Tavener's most convincing late works, but not least for the wonderful, atmospheric cello solo line (Josephine Knight) that intermittently surfaced and occasionally took apocalyptic flight on its own.

It was a cello that also mesmerised in the first half. Guy Johnston, a former BBC Young Musician of the Year, was on hand to offer the most riveting and ravishing performance of Tavener's celebrated quasi-concerto The Protecting Veil. Armed with Johnston's serene, pristine beauty of tone, this was the most persuasive performance I have yet heard, large because both Johnston and Atherton eschewed all histrionics and allowed the piece to speak for itself, without special pleading.

Eloquent, spiritual in its own way, unerringly beautiful, and here without any longueurs, this performance, wise, honest and thoughtful, proved utterly transporting.