THE meaning of "Cumnock" is probably the confluence of two waters: the Glaisnock and Lugar rivers; while a "tryst" - the kind of word you might associate with Robert Burns - historically denotes a meeting of two persons, more especially a secret confluence of two lovers.

The Cumnock Tryst, the new festival founded by the composer James MacMillan, now in his fifties, in his home town in Ayrshire, lived up to its name (he prefers Tryst to rhyme with the German Geist rather than English wrist or gist). It proved a meeting of people galore. For the Festival Mass and the initial concert by Harry Christophers and The Sixteen - embracing three new settings of the Stabat Mater - it was standing room only.

Then for the Festival's president, the Ayshire (West Kilbride)-born violinist Nicola Benedetti, just 27, who gutsily and ravishingly played Bach's massive D-minor Chaconne, and joined in a work by MacMillan himself at the stately 18th-century Dumfries House, listeners had to stand, patient and rapt, in the main entrance hall.

In some ways, MacMillan as artistic director, aided by his wife, Lynne, as chairman, dedicated this festival to a key figure from Cumnock's history: John Crichton-Stuart, the third Marquess of Bute (1847-1900), who, on inheriting Dumfries House, set himself not least to providing a church, St John's, for the large Roman Catholic contingent in Cumnock.

Here, The Sixteen brought Russian-born, Estonian, and British composers together; and, not least, performed the music of John Sheppard, contemporary of Tallis, Taverner, and Tye, and seen by some as, if not the greatest, certainly the most original of the composers of the early to mid-Tudor period.

Equally, Matthew Martin's new treatment of the Stabat Mater was the most original, while the most powerful without a doubt was that of Tõnu Kõrvits, who came from Tallinn for the occasion. The tenderest was that by Alissa Firsova, brought up in England by two famous composer parents, Elena Firsova and Dmitri Smirnov.

The marvel of this festival was the sheer intelligence, wisdom, and generosity of its planning and organisation. The staffing by purple-chemised volunteers ("I'm here to help") was terrific. MacMillan chose several contrasting venues (he intends the Festival gradually to reach to others, and to the country villages beyond): the Old Church of Scotland building on the square, as well as St John's; the school he himself attended and to which, he says, he owed so much musically; the manor.

Central was the Dumfries Arms Hotel, which provided, as the host, James Naughtie, remarked, a "cabaret-like" venue. That same night, violin music with a difference took the floor: a series of pieces, Bach-related or connected with the famous musical theme La Folia - but with Corelli or Geminiani intermixed with a series of striking quasi-variations - "decompositions" is a term used - by contemporary Scandinavians or the performer himself, locally born Ian Peaston.

For all the computer-generated extra effects - many of them, especially the violin remixed in bass vein, often with a kind of woody battuto feel, teased the ear - one warmed most to the music when Peaston played just a few items straight. A little more of that (one folk tune near the close was absolutely sensational) might have helped generate contrast with the bold exploration and ingenuity.

Four of The Sixteen, led by Eamonn Dougan, stayed on as artists-in-residence. I can say, from putting myself through the same hoops, that Dougan's handling of a "come and sing" group in repertoire from Purcell and Boyce to "Bye, bye, blackbird" was a revelation: focused, ever-incisive, putting his finger instantly on ways of improving performance, and reaching out to engage his charges. But, more importantly, this ad-hoc ensemble, which MacMillan hopes "might form the basis of a Festival Chorus in future", is already that: the calibre of participants in all voices was staggering.

But, just as MacMillan has turned out since his youth with a tin whistle in bands at ceilidhs (hence the huge input of folk music, and folk-treatment, in his material and his actual methods), so he can recall how his maternal grandfather, a musical miner in this characterful but now no longer mining town, placed a cornet in his hands as a small boy and turned him into a brass-band player.

This was also a festival of thank-yous: to the town of Cumnock, in good and bad times historically, and to which he wanted to bring an event that might bring something of the spirit of Benjamin Britten's Aldeburgh Festival, or Sir Peter Maxwell Davies's St Magnus Festival in Orkney; to the school, to which he brought the superb Scottish Chamber Orchestra for a cracking and shivering polar work, Arktis-Arktis, by the Swedish composer Karin Rehnqvist, who was present; to the art of brass-playing; and with it, to the young (four invited schools turned up for the Arctic event).

Hence, there was not just an entertaining final triple concert, including riveting "lesser" Bach and a (slightly contorted) new commission from a MacMillan protégé, Jay Capperauld, by brass quintet (perhaps the ordering of events didn't quite work here); but for me the highlight of the whole four days was an appearance by the National Youth Brass Band of Scotland under its new conductor, Russell Gray.

What a sensation they are. All credit should be given to the Cumnock Academy Brass for a key part in the finale, and to Greenmill Primary School string orchestra for a wee piece specially written for them by the man himself. But it was the National ensemble that took my breath away. Even without the addition of the Norwegian tuba-player Eirik Gjerdevik (ever-beaming, he towers over us like a Goth of old) to play Vaughan Williams's late Tuba Concerto (brilliant), and take a turn in other works, these young performers hit everyone, it seemed, for six.

In Elgar (his Severn Suite, late refined for brass alone), Howells's Pageantry, and John Ireland's A Downland Suite, they impressed; in MacMillan's brilliant short work Jebel they dazzled. Just to watch and hear these trumpets, trombone, and various-sized euphoniums and tubas at work was an education. Their Wagner, the wedding procession from Lohengrin, had the crucial long line, if perhaps not enough colouring. Above all, Gray's leadership and interaction with his players (as a lad, he was himself a member) were pure joy.

If you venture to Ayrshire early next year you can hear the Trombone Concerto by Ferdinand David's (Mendelssohn's concert master) (January, Ayr Town Hall), and the Double Bass Concerto, Op. 3, by Serge Koussevitzky - a bassist himself (February). You won't get those anywhere else. But if you miss them, there is always the 2015 Cumnock Tryst to sample. You won't regret it.

The next Cumnock Tryst will run from 1 to 4 October 2015.
www.thecumnocktryst.com