Benjamin Britten died 20 years ago on Wednesday and, as always with anniversaries, it was time for taking stock. Britten died at an age (barely 63) when some composers (Janacek, Vaughan Williams) were still settling into their stride. You can't help wondering what might have emerged from another decade or two, teased by the fact that although his final years were dogged by illness, his last works - Phaedra and the Third Quartet - show no sign of diminishing power. On the contrary, they introduce a focus and economy of means that could easily have developed into a whole new musical vocabulary, given the chance.

In any event, the past 20 years haven't disproved the claims made for Britten's durability and stature in his own lifetime. He still stands as the greatest composer this country has produced; and even if the town council of Aldeburgh did prefer a municipal bird-bath to the idea of erecting a Britten memorial on its seafront, the composer's music lives unchallengeably on. Not least on Wednesday night, which saw an extraordinary commemoration of the 20th anniversary in a sold-out concert of the War Requiem at Westminster Cathedral. Steuart Bedford conducted a vast orchestra and chorus (amassed from students at the Royal College of Music and 17 other conservatories around the world). The young line-up of soloists was superb: a poised, squall-free Russian soprano, Iana Ivanilova; an immaculate, light-textured English tenor, Mark Wilde; and a German baritone, Johannes Beck, who sang with a soft, seductive darkness that was wonderfully attractive. Names to listen out for, all three.

Bedford's methods of handling both his seething student forces and the cathedral's black-hole acoustic involved an element of self-denial that capped the climaxes, stopping them becoming the great, pulse-racing noise they ought to be; but this was a formidable exercise in control, with a purity and freshness that belied any idea of the Requiem as "Sixties" music. Which of course it isn't. It transcends its period, as it transcends the schoolboy clum-siness of Wilfred Owen's poetry.

There was more remembering at the Wigmore Hall last week in a memorial concert for Peter Stadlen (1910-1996), music critic of the Telegraph until the early Eighties. Stadlen was a critic of the old school: erudite, uncompromising, sternly wise, and with a particular authority that came from his first-hand experience of music in pre-war Vienna. Originally a pianist, he studied with Webern and gave the first performance of Webern's compact but eventful Variations op 27, before his career was cut short by the Third Reich and he fled to England. This Wigmore concert began with a ghostly 1940s recording of Stadlen playing the Variations, prefaced by a fascinating old BBC talk in which he analysed them for considerably longer than they take to play. How things have changed at R3!

Otherwise, the seriously mittel-European programme featured songs by Berg and Schubert, warmly played by Imogen Cooper and sung by a young mezzo, Jane Irwin - who needs more interest, intensity and pace in her delivery, but who makes an essentially attractive sound with clean, pure tone. And there was also a promising young Austrian pianist, Christoph Berner: though he made the Third Variation of Beethoven's op 111 Arietta sound too much like an 1820s Viennese Charleston for my liking, he was a model of style and idiom in Schoenberg's Three Pieces op 11.

Last Sunday was the start of Advent, when the Christian year begins. Its music embraces the ecclesiastical equivalent of what German lieder-writers knew as "sensucht": longing, in heightened expectation of the coming of Christ. Pure Advent music is probably the most evocative in the whole church calendar, and almost nothing in any genre of music- making attacks the base of my spine so surely as the Palestrina responsory "I look from afar" that prefaces all good Advent carol services. It did the job this year at Clare College, Cambridge, where Timothy Brown directs one of the best mixed-gender chapel choirs in the university. The Advent carol service here was a real feat of performance, in an acoustic that doesn't cherish singing voices as it does at King's next door.

Fresh, vigorous and striking, it was all the things Covent Garden's yet- again-revived Tosca is not, despite forcefully deliberate conducting from Edward Downes. There are new cast-members in Keith Olsen, who sings a two-dimensional Cavaradossi, and James Morris, whose Scarpia is his first Italian role at the Garden and inhibited by too much of the discreet under-emphasis of his famous Wotans (what works for Wagner doesn't necessarily do for shabby little shockers). Galina Gorchakova's Tosca is nicely sung but without enough weight, and she doesn't exactly give herself to the drama of the role. Her ascent to the fatal parapet is more decorous than desperate. And for "Vissi d'Arte" she drops right in front of the prompt box, taking far too keen an interest in the man inside: she looks like somebody short- sighted watching TV. Surely she knows the words by now?

The Philharmonia has begun an ambitious two-year project to tour and record the works of Gyorgy Ligeti, the most engaging and, yes, lovable figure of the central-European avant-garde elite. Called Clocks and Clouds after a seminal Seventies score for orchestra and voices, it will survey the meetings of mathematical order with impressionistic fantasy that preoccupy Ligeti's work, and (especially) the different approaches he has made in 40 years of writing towards the objective of a music that defies the sensation of passing time. His first scores to make their mark were dense with tiny, vigorous movement so compacted that it becomes texture rather than a means of propulsion. Then came a more open, spacious, tonally melodic kind of writing, exemplified by the Cello Concerto which Esa-Pekka Salonen conducted in the opening concert at the RFH on Thursday (soloist David Geringas). It isn't a real concerto - there's no dialogue to speak of between solo and accompaniment - but the out-of-time effect is undeniable. And the later San Francisco Polyphony, also in the programme, is a development of the same idea: more obviously moving, but in the way that random objects would move in a shaken vat of jelly, making images of fleeting order out of general chaos. This is fascinating music; and there's more tomorrow when the Philharmonia plays the Requiem - which made Ligeti's name when Stanley Kubrick used it for the soundtrack to 2001. Kubrick apparently didn't ask permission because he assumed the composer was dead. Well, they usually are, aren't they?

'Tosca': ROH, WC2 (0171 304 4000), continues Mon & Wed.