One accusation that could never be levelled at the Cheltenham International Festival of Music is that it comes "off the peg". At this time of year, with the country bristling with festivals, all too many of them present sameness and tameness. But when festival directors are asked to turn cart-wheels on a high wire to make the books balance, it's not difficult to see why: repeated concerts spell amortisation of costs. But not interesting festivals. Cheltenham is an interesting festival.

With a composer as artistic director, it comes as no surprise that new work should figure prominently. But what is surprising is the quantity and the notable quality. In 15 days, there are no fewer than 20 world premieres, with two major British premieres. Michael Berkeley, displaying a little of his own "private passion", insists that every programme must contain 20th-century music. Fudge is usually the rule - just drag up the most palatable work, whether or not it fits the programme. But this is decidedly not the case here: new work has not only been chosen carefully but is of equal importance, placed in a context that supports and illuminates.

Of course, not all new works turn out as expected and Vic Hoyland's A- Vixen-A was a case in point. Originally commissioned by the BBC for John Drummond's final Prom season, ill-health prevented the work being written. Now we have a substantial 30-minute piece for substantial orchestra including a very large kitchen- sink department. With such forces, the platform of Cheltenham's Town Hall was not large enough to accommodate everybody for last Friday's concert, so the BBC SO was placed on the flat - sight-lines compromised but the sound, normally a mush, magnificent. Hoyland's work should have been placed between Brahms's Second Symphony and Mahler's Lieder eines fahrenden Gesellen - the usual sandwich technique. But an inspired last-minute decision was taken to change the order to Brahms, Mahler, Hoyland - which said everything about debts: Mahler's to Brahms, and Hoyland's to Mahler.

Hoyland, a product of the heady 1970s York University Music Department, has written a powerfully expansive work. It evokes the spirit of Mahler in its use of predominantly dark harmonic colours, sensuous use of sustained strings, and high muted trumpet, while embracing the force of Messiaen with gongs, tam-tam, marimba and crotales. An oddly successful (and original) synthesis of German and French sensibilities refracted through British eyes.

Context said it all again in a ravishing late-night concert given on Saturday by Gothic Voices, Christopher Page's ace team of four specialising in the wondrous mists of ancient time - medieval a cappella vocal music - in Cheltenham College Chapel, a mini King's College, Cambridge.

What an ear-cleanser! Nearly 1,000 years of music - with a gap of about 500 years in the middle - provided a magically soothing end to the day. Hildegard of Bingen, that mystic Abbess of 1098-1179, rubbing shoulders with "anon", Guillaume de Machaut - the experimental master of the 14th century - and our own Bayan Northcott. Northcott's Ave regina clorum is a cunning ficta based on one of the Marian antiphons. From an opening straight rendition of the plainchant, Northcott gradually absorbs and translates the material in ways both contemporary and medieval, intelligently illuminating the closeness of the two worlds in a pleasingly compact piece.

Another compact but dully derivative work found its way into the programme of the Orchestra of the Age of Enlightenment earlier that same evening. In fact, the Choir of the Enlightenment took on the task - His Winding- sheet by Betty Roe. Context in works of Bach provided no help and perhaps the inexplicably small audience served to undermine the choir and OAE's usually spirited approach. Peter Harvey and Ruth Holton, soloists in the cantatas, sang well, while Paul Nicholson officiated from organ or harpsichord, never quite sure, it seemed, whether to face us or them. Annette Morreau