GILES SWAYNE'S credentials include a love affair with Africa and a period of time as composer-in-residence to the London Borough of Hounslow. So he has seenlife, and produced from it a body of work that dances with African rhythms and adapts sophisticated thinking into terms accessible to listeners on the westerly equivalent of the Clapham omnibus. For years his calling-card has been a piece called Cry, written in 1979 for 28 solo voices, with a combination of technical virtuosity, textural richness and popular appeal that set a lingering stylistic benchmark. But in truth, there hasn't been a lot of Swayne about in recent years, and it had begun to look as though Cry was an unrepeatable achievement - until news broke of a new commission that reached performance at the Spitalfields Festival on Monday. Called The Silent Land, it was one of those rare things, a private commission - from a Cambridge woman, Phyllis Lee, who wanted something for the choir of Clare College to sing in memory of her husband. And the result was a grand setting of memorial texts for 40 solo voices in the manner of Thomas Tallis's Spem in Allium, which made an obvious companion piece on this same Spitalfields programme.

Now, there's no mistaking a choir which is about to sing you Spem in Allium. For one, its members will be carrying scores as big as table- tops (those 40 staves take up a lot of paper). For another, they'll be looking worried. It's a daunting piece and it rarely works: the texture is too dense to sound like anything but sonic mud. So Swayne's "hommage" had kamikaze qualities: ambitious but perverse. And though it recognised the problems of the texture, adding a solo cello (Raphael Wallfisch) to seduce the listener's ear into reflective pools of purer sound, the cello/voice relationship never felt quite convincing or entirely necessary. The score seemed fractured, not so sure where it was going. And I doubt if many of the students/young professionals who sang it at Spitalfields knew either.

But there was more Swayne on the programme that worked infinitely better: his Missa Tiburtina, written in the mid-1980s and a strong, secure piece that makes forays into the Renaissance past from a present of fiercely percussive jazz-like ostinati and afro-syncopation. Less a spiritual statement than a social one, there's an agenda to this writing and it's angry - fuelled with the attack of broken syllables, and a peculiarly gutsy Benedictus. At Spitalfields, it registered with clarity and purpose under Tim Brown, one of Britain's most effective choir conductors and a prime custodian of the tradition that makes Oxbridge chapels famous from Seattle to St Petersburg.

Not that they don't have a tradition of their own in such places, as heard on Tuesday when the St Petersburg Chamber Choir - by general reckoning, the finest (professional) choir in Russia - opened this year's City of London Festival. The venue was St Paul's Cathedral, where the acoustic is something you swim in rather than project through. But the slow swirl of Rachmaninov's Vespers around the dome on Tuesday was superbly atmospheric, strong on colour if not detail; the voices were immaculately balanced under Nikolai Korniev; and it was a joy to hear those Russian basses float down effortlessly to unblemished, cushioned landings on their bottom As. Steeped in the ritual chant of Orthodoxy, this music isn't typical of its composer, and there always seems, to my ear, something "assumed" about it: the work of an informed observer rather than devout believer. But there's no denying its hypnotic charm; and if Rachmaninov had only had the foresight to enlarge its ceremonical austerity - with fewer, even slower notes repeated more insistently - who knows? He could have made it really famous - like John Tavener, who had a touching premiere on Thursday at Marylebone's Hellenic Centre.

Called Depart in Peace, it was written for the strings of the BT Scottish Ensemble, plus a solo voice (Patricia Rozario) supported by the sitar- like underlay of an Indian tanpura; and it came in the familiar Taveneresque form of alternating verse/refrain blocks in a patience-testing cycle. But the personal nature of the piece - in memory of Tavener's own father - gave it a certain edge. Rozario sang beautifully - a small but stylish voice. And things livened up when a telephone rang in the 16th (or was it 17th?) cycle: a message, no doubt, from the BT Scottish Ensemble's sponsors.

Ireland has too small a population to sustain a year-round opera calendar, but things look up when the Wexford Festival gets going in the South; and there's a quasi-Wexford of the North at Castleward, which has never been as big or as adventurous as Wexford but still simmers with potential. Castleward is an impressive Georgian pile near Belfast and remarkable for being architecturally two-faced. Its original husband-and- wife owners couldn't agree a style, so one side is classical, the other gothic. Unsurprisingly, the marriage failed - but left as its legacy some odd design, including one room whose Strawberry Hill pendant vaulting is so overscaled that Betjeman likened it to living underneath the udders of a cow. The space now used for opera is less fanciful: it's in an adjoining stable-block that makes for a long, thin auditorium with a cramped stage.

But the Traviata playing there last weekend triumphed over its confinement, with a clever, mirrored set, a neat production, and disarmingly good singing from Elizabeth Woollett in the title role. Secure, affecting, with a forceful top-reach, it fulfilled the promise of the Eurydice I first heard her do some years ago for ETO. Since then she's made her mark in concert and at ENO. And if her Violetta works on bigger terms than Castleward (it should) then she has something powerful to sell abroad.

There are some strong ladies in the new Falstaff which has been playing to delighted if damp audiences at Garsington. And though it's one of the simpler shows that play there, done against the side of the house and without the focus of a purpose-built set, it's actually quite close to what we know Verdi intended: especially in Act II where his instructions were for the stage to be bare, so the action of the main groups - at the screen, the basket and the window - remains distinct.

The action here, directed by Stephen Unwin, is agreeably precise with clean, sharp comedy and singing actresses like Elizabeth Gale and Mary King who relish their texts. Robert Poulton's Falstaff may be flabby of figure but is keen of voice. And the conductor Stephen Barlow keeps the pace alive. The only pity is that the whole thing can't retreat into the depths of Garsington's gardens for the Windsor Forest scene. It would be magical. But even damper.

City of London Festival: various City venues (0171 638 8891), to 16 Jul. See 'Going Out', page 10, for ticket offer.