OPERA / Light hand through the darkness: Judith Weir's opera Blond Eckbert opens next week. Bayan Northcott profiles a composer of endless surprises

For a wind quintet, Out of the Air seemed a neat enough title. And as the five young players unfolded its faintly Ligeti-like textures of sustained notes and pulsations occasionally interrupted by abrupt interjections, the music's vestigial substance did indeed sound as though it had been conjured out of almost nothing. Yet the 10-minute structure was evidently well heard and more than a little teasing in its evasion of expectations. For, just as the ear was beginning to hanker after something different, there was a pregnant pause during which the bassoonist portentously raised a large, cork-shaped mute and plugged the instrument. And then? With a single staccato chord, it was all over.

Judith Weir was still only a 21-year-old undergraduate studying with Robin Holloway at the time of that London first performance in February 1976. Earlier lessons with John Tavener had already taught her much, but she was to withdraw the resulting pieces from her catalogue. Out of the Air, by contrast, she has retained doubtless because it already suggests her characteristic clarity of sound, economy of means, objectivity of expression, liveliness of dialectic and theatricality of gesture - though, in relatively abstract form, uncoloured as yet by the idiosyncratic selection of musical images and idioms from so many cultural traditions which she has been gradually assembling, mosaic-like, ever since.

Admittedly, the assumption that she remained an amusing lightweight seems to have lingered at least into the mid-1980s. This is an assessment at which she may partly have connived through her sometimes self-deflating titles. Several Concertos (1980), for instance, turned out to be three short movements giving successive prominence to the players of a mere chamber trio. But her quiet confidence of a longer-term synthesis also seems to have been masked by a couple of other tendencies. One was an apparent determination from the start to master in her own way each of the basic elements of music in turn.

So several works of the late 1970s were almost purely harmonic in interest - as in the rippling chord sequences of the sextet, King Harald Sails to Byzantium (1979). In the early 1980s, the spotlight swung towards gesture, and pieces such as the violin and piano duo, Music for 247 Strings (1981), jerk forward spasmodically in rhythmic unison, in a manner analogous to Messiaen's abrupt birdsong figuration. Only since the late 1980s, in such linear studies as the piano quartet, Distance and Enchantment (1989), has Weir turned to the evolution of a more sustained melodism. The other complicating tendency in her progress has always been her affinity for seemingly marginal or 'alternative' musical sources. Just as Stravinsky - always a strong presence in Weir's background - proceeded from a disinclination amounting to inability to further the luxuriant mainstream language of European late-Romanticism, so Weir rejected the orthodoxies of post-war avant-garderie. Instead she cleaved on the one hand to a not-so-serious post-Cageian Experimentalism, and on the other to various regional art and folk-music traditions. As might have been expected from her family roots, sprightly touches of the Scottish vernacular have been liable to inflect her invention at any time. But, as with her technical explorations, the other sources have tended to emerge in specific groups of works.

In fact, most of the overtly Experimental pieces were among those withdrawn early. But in the mid-1980s, there was a Chinese preoccupation, initiated by the engagingly stylised music-theatre piece, The Consolations of Scholarship (1985), followed in the late 1980s by a brief Spanish phase and a more extensive involvement in Balkan sources, exemplified by the beautiful Croatian folksong study, I Broke Off a Golden Branch (1991). And before any of these, there had been a curious Bayeux Tapestry obsession - not so much with any surviving scraps of Anglo-Saxon music itself, as with parallels between musical process and story-telling. One result was Weir's first work to bear the subtitle 'Opera'. True, anything less obviously prescient of the focal function opera would eventually play in her development than King Harald's Saga (1979) could hardly be imagined. Here is economy of means with a vengeance, for this entire 'Grand Opera in Three Acts' with its eight principal roles lasts just 10 minutes and is scored for a single, solo soprano. Yet the skilful disposition of vocal register to evoke contrasting characters and musical forms proves no mere party trick, for the work's conclusion also discloses a mood of stoic endurance to be detected beneath the brightest surfaces of Weir's subsequent stage works.

So, the contrasting scene structures of her first full-length music-drama, the deservedly praised A Night at the Chinese Opera (1986), may have been nicely devised to allow for the most varied and vivacious packaging of her accumulated musical resources. But we are rarely allowed to forget that the sometimes comic ironies of its Chinese-box, play-within-a-play narrative take place against the background of an implacable tyranny. In her second opera, The Vanishing Bridegroom (1990), Weir may again evade convention by casting her libretto in the form of three interlinked Scottish folk tales, which incidentally allow for a striking chromatic enrichment of her hitherto pan-diatonic harmony in the first act, and a newly sensuous indulgence in static texture at the beginning of the second - to say nothing of a dramatic outwitting of the Devil in the third. But somehow the threat of dark forces remains to the end.

And her new two-act commission for English National Opera, Blond Eckbert (1993), draws a sinister magic from yet another of her long-term preoccupations: the uncanny amalgam of folklore, pantheism and the supernatural that compounds the world of early 19th-century German Romanticism. Ludwig Tieck's seminal novella, Der blond Eckbert, from which she has drawn her libretto, also allows her to exploit once more the dramatic ironies and ambiguities of a story-within-a- story. The first act is largely given over to a retelling by the protagonist's wife of the fairytale circumstances of her childhood - circumstances the increasingly psychotic Eckbert finds himself reliving in the second act as he gradually uncovers the incestuous basis of their marriage - though Weir handles the denouement with characteristic despatch and understatement.

Nor will one discover a moment of pretension or wooziness in her setting. Tieck's hallucinatory precision of detail is matched point for point by the needle-sharp imagery of Weir's invention. As the long, leaping line of the opening pages immediately reveals, her principal concern remains the generation of melody, but inflected and coloured now, as it has been since her vivid overture, Music, Untangled (1992), by a new delight in ever-changing orchestral doublings. And it is in such contexts as the latest opera that her rare gift for finding fresh sounds and procedures in the most basic musical elements takes on an ethical dimension. Like Haydn, whom she once described as the ideal composer and possibly most takes after in spirit, if not in idiom, she seems to imply that the proper cherishing of the modest things in life may not only help us to endure much that remains immutably dark, but can also yield an amazing amount to enjoy.

Opens Wed 7.30pm London Coliseum (071-836 3161), then 26, 29 April, 4, 12, 14, 18 May. Radio 3 relay 11 May

(Photograph omitted)