Classical: Going strong; and on and on

La Monte Young: 'The First Blossom of Spring' Barbican, EC2 Chicago Adelphi, WC2 John Rutter Cambridge Clare College

In photographs he bears an odd resemblance to a rotting vegetable. In real life he's a superannuated biker: black bandanna, dark shades, grizzled beard and torn-off denims. For a man of 63, he's quite intimidating. But in Britain we don't often get the chance to be intimidated by La Monte Young, legendary guru of the New York City avant-garde. So his appearance at the Barbican on Tuesday was a definite occasion. And the more so because he appeared (a) in full kit, (b) with his longstanding wife and collaborator Marian Zazeela dressed to match, and (c) with his ensemble Theatre of Eternal Music, who have never played in London before.

Should you wonder about the name of this ensemble, the key word is "Eternal" - for La Monte Young has no truck with the transitory. The idee fixe of his creative life has been music of (as he unassumingly calls it) extended duration. In other words, pieces that go on for ever. Literally. Born in a log cabin in a remote American farming community, his formative musical experiences were the sustained sounds of the wind whistling through wooden eaves, and the hum of electric generators. When he made the leap from farming to art during the 1950s, he carried those experiences with him - into pieces like Composition 7, which was two notes held, as indicated, "for a long time". Another piece required stones to be placed on the pedals of an organ, and left there for a week, presumably with the power running. As his confidence increased, he touched the ultimate with something called Dream House (a sound installation in Manhattan) that lasted for six years.

In the circumstances, we were fortunate that the piece he brought to London, The First Blossom of Spring from The Four Dreams of China (Melodic Version), only ran for a couple of hours. But then it was nothing more than the gradual compilation of a four-note chord, played with shifting emphases by a solemn semi-circle of cellos and muted trumpets. Despite the added interest of coloured lights, devised by Zazeela, audience attention started to splinter after the first hour. And I daresay that a good few, even of those who made it to the end, will have wondered uneasily what the non-melodic version must be like.

You may be wondering why I bother to report this, and it's true that in the greater scheme of things, La Monte Young is a marginal eccentric. What he does now is of limited interest and less value. But back in the 1960s, he earned a place in history as the so-called father of minimalism. And though I think that statement must be qualified - because minimalism has come to be a matter of sustained rhythm, whereas Young's work is preoccupied with sustained pitch - it bears some scrutiny. Young introduced to Western music the ideals of stasis, of "pure" sound, and of work which was less concerned with end results than with ongoing process. These things were, and are, significant. And they lock Young into the achievement of, on the one hand, John Cage, and on the other, his fellow-traveller Terry Riley. It was Riley who, in the mid-1960s, brought rhythm into the picture and then truly lit the minimalist rocket, leaving Young behind. But to experience the floating non-directionality of The First Blossom - originally devised in 1962 - is to feel that Young was on to something.

Personally, I wasn't bored at all. My ear was wonderfuly seduced by its intensive scrutiny of pitch relationships. And I was fascinated by the coded signals that pass between the players to determine how the pitches weave into (or out of) focus, how the dynamic rises (or falls), and where the periodic moments of "performed silence" intervene. In fact, I found it therapeutically alluring. But then, I speak as someone who, from early childhood, has believed that the domestic vacuum cleaner is the sound to which all music aspires. It's as well I never got round to bandannas.

I never got round to sheer black Lycra either, which is probably why I don't feature in the cast-change for Chicago: the 1970s American musical, long- running at the Adelphi, whose wardrobe is nothing but. Readers of this page will know that I rarely venture into musicals unless they're by Stephen Sondheim; and Chicago certainly isn't that. A diluted-down revisitation of Brechtian vaudeville, with just the thinnest veneer of moral outrage and obligatory spot of cynicism, it's not so much a great piece as a great performance. So the cast is all. And without its two former stars, Ruthie Henshall and Ute Lemper (whose presence reinforced those Brechtian origins), it might have faced problems. But the new cast has one stunning asset, hence my interest: the extraordinary Maria Friedman, whose dynamic energy and brilliant stage-sense guarantees a sexy, sassy, high-precision show. She doesn't put a foot wrong, or a note. It's a complete performance in a small frame packed with raunchy cuteness. When she sings you listen: every word tells, clean and purposeful, and with a breath-control that any opera singer would be pleased to duplicate. How she can be so animated and produce a pure, firm sound, I can't imagine. But she does, and it's a joy. I could have listened to her for La Montian durations.

Otherwise it was a choral week. We're into Advent, the season of Messiahs and the two Johns - Tavener and Rutter - who reign jointly these days over matters musical and Anglican. King's Cambridge sang the Rutter Requiem on Wednesday at the Barbican, and because I was at Chicago I didn't hear it. But I did hear a quantity of Rutter last Sunday at Clare College Cambridge - where Rutter was once director of music, and where his successor, Tim Brown, has nurtured the chapel choir into one of the best mixed-voice ensembles in the university. As always, I felt ambivalent about this music: it can owe too much, too obviously, to Faure, Walton, Howells or Britten. It can also be a touch sweet. But I can't pretend I don't enjoy it. Rutter has a real melodic gift, a sense of line, a feel for texture. Even at his lightest, he's incredibly engaging. And I was engaged, too, by his new piece for choir and flute, Musica Dei Donum that the Clare Choir sang a few weeks ago in a concert at Smith Square. It's an odd combination, choir and flute, that you wouldn't expect to work. But it does. And what's more, the carol commissioned for King's on Christmas Eve this year is another choir and flute score by another Cambridge-linked composer, Giles Swayne. Is this just coincidence? Or something in the water?

'Chicago': Adelphi, WC2 (0171 344 0055), booking to 29 May.