First there was Giordano's fin de siecle Fedora, with its pre-revolutionary Russian plottings and its arias in praise of the push-bike and the aphrodisiac qualities of the tandem. Now there is Housewatch's Imaginary Opera, with its multi-media mix of live music, film projection and, yes, bicycles. Not that it is really much of an opera, imaginary or otherwise; there is no singing for a start - but much the same could be said of Covent Garden's recent revival of Fedora. Then again, even in the current rail dispute, bikes are hardly as omnipresent a mode of transport here as they are in Japan, where the piece was premiered two years ago. Still, with their monotonously mechanistic means of self-propulsion, bikes don't make a bad metaphor for the relentlessly recycled repetitions of the composer Steve Martland, whose string piece, Crossing the Border, provides the live soundtrack to Housewatch's open-air performance in and around the Royal Festival Hall on Saturday night.

Martland's music mixes minimalism and agitprop pretension; 'For Steve Martland, all stages of composition - production, reproduction and consumption - are as political as they are inextricably entwined,' read the liner notes to one of his CDs. 'His ideal: to make the world a better place.'. It makes a fitting curtain-raiser to Meltdown, the South Bank Centre's new composer-centred summer music series, which this year is hosted by Martland's musical mentor, and leader of the old Dutch new wave, Louis Andriessen.

Where last year's guest programmer, George Benjamin, offered what was virtually a short course in musical modernism, the affable Andriessen has simply seized the chance to invite a few friends round for a party. With friends like Peter Greenaway (with whom he is currently collaborating on an opera), Philip Glass (who brings his new live score to Cocteau's La Belle et La Bete) and Gavin Bryars (still dining out on the delayed success of Jesus' Blood), it all looks like being great fun, but what does it add up to? Sunday's opening marathon is typical - an eight-hour lucky dip in which quantities of energy, enthusiasm and endurance outweigh any enduring qualities in the music itself. Luckily, Andriessen himself is made of sterner stuff - his tough, sinewy, abrasive music, welded from a personal mix of Stranvinsky, jazz and minimalism, all put at the service of big issues like the nature of time and speed, and the boundaries of music and state. The highlight of the series should be the concluding concert performance of his Robert Wilson collaboration De Materie, a four-part theatre piece on ship-building, atomic theory, mysticism and Mondrian.

Imaginary Opera: Saturday 10:30pm RFH. Meltdown continues to 3 Jul, South Bank Centre, SE1 (071-928.8800).

(Photograph omitted)