MUSIC / Light on the trigger: Stephen Johnson on works by Stephen Montague and James Dillon

FROM time to time, classically-raised English musicians feel the need to let their hair down. Sometimes it works, more often it's horribly embarrassing; but the implication remains the same: either you're serious or you're not. It takes a composer from another background - the American Stephen Montague, for example - to show how to be serious and uncorseted at the same time.

Montague's 50th birthday concert last week offered several such lessons. First he achieved the near-impossible by turning the Purcell Room into a place of wonder. Listeners arrived to find the stage soaked in hazy lighting and filled with the real-life grunts, clicks, whoops and chatterings of Montague's Synthetic Swamp. Gradually, the Smith Quartet and the flautist Jos Zwaanenburg joined the recorded swamp-creatures with noises of their own - the result, a piece called Eyes of Ambush.

The remaining mixture was wilder still; virtuoso 'Romantic minimalism' in the piano piece Paramell Va, reworkings of American hymns, folk-tunes and marches in the aptly named troubador-meets-scat piece Boombox Virelai (yes, the Hilliard Ensemble did make it from the Wigmore Hall on time, and in breath), and an energetic memorial tribute to two composer friends, Barry Anderson and Tomasz Sikorski, in String Quartet. Montague's aim is a bit blunderbuss-like: ideas scatter in every direction and not everything seems to hit the target. But there is more to him than clowning - here is a post-minimalist who can surprise, challenge, amuse and even move. The echoes of desolate Sikorski at the close of String Quartet were just the thing to end Part 1, and to send one to the bar thinking - as no doubt the deaths of Anderson and Sikorski at around 50 made Montague think. Long may he continue.

Single-minded seriousness with a vengeance was on display at the first British performance of James Dillon's Introitus at St Giles's Cripplegate - if 'display' is quite the word. Dillon's programme-notes, with their talk of 'palimpsests', 'generic taxonomies', and 'attack / delay transients' busily 'citing their own deconstruction', give the impression that he doesn't much care whether you understand his music or not - there's a suspicion that he might be offended if you did.

But while the inter-reactions of live string ensemble, tape sounds and live electronics may be dense and intimidatingly complicated on paper, at heart Introitus is direct and compelling. Not only are many of the musical events arresting in themselves, there is a current that carries the ideas irresistibly forward, even when it seems to be running in many strands at once. This is one of the few new music concerts I can remember in which playing the work twice - albeit with an interval and a talk in between - was both welcome and revealing. Still, a powerful, beautiful, utterly original work like Introitus deserves to be more widely heard than by a small group of cognoscenti, though preferably with the same performers - Richard Bernas and Music Projects, London. Dillon is quite possibly one of our major composers, and the greater the number that can be allowed to discover that, the better.