Classical: Meltdown Queen Elizabeth Hall, London Gogmagogs Gigagain Bridewell Theatre, London

The first weekend of Laurie Anderson's Meltdown Festival at the South Bank climaxed on Sunday afternoon in the Queen Elizabeth Hall with 100 violinists turning on the heat. Everything had its story, and there were no predictable endings. Writer and broadcaster Ken Nordine told us about Rog (Oh, Here's Rog) who "played the organ in church... a strange guy, stranger than strange". Dean Brodrick's score calls for all sorts of effects, including bouncing the bow in imitation of applause, but when Gidon Kremer took to the stage for the world premiere of George Pelecis's Very Serious Variations on the Etude No 2 by R Kreutzer - prefacing it with not-very-serious comments about the rigours of practising - the temperature rose even higher. Pelecis's piece was immense fun (lots of jokey tuba and contra-bassoon writing), though less memorable than a dazzling, unscheduled and unaccompanied Tango-Etude by Astor Piazzolla. Back on schedule, BK Chandrashekar treated us to some curvaceous south Indian Karnatic music, fiddling away while stage-hands shifted chairs and the young members of the Indian Strings Chamber Orchestra prepared to join in. RN Prakesh slapped his claypot, we tapped our feet, and the 100 violins entered the spirit under Chandrashekar's hand-clapping direction. Joe Townsend's A Cat, a Horse and a Tree had the orchestra sound like a Romanian gypsy band and the grisly "Readings from the Encyclopaedia of the Violin, 1921" - intoned by Nordine and Anderson herself - included lots about dried-out intestines.

Could things get any stranger, I thought. Well, there was Anderson's "Tape Bow Quartet", where four ladies each drew a length of recorded tape (in place of bow hair) across a tape-head (in place of strings). Fragments of speech spat and spluttered while the quartet swayed this way or that. Then there was The Sea (for John Cage), where Simon Wills conducted a fragment of the second violin line from the first movement of Debussy's La Mer, measuring the missing bars in his head and conducting them as meaningful silences. A Dummy Duet had Laurie Anderson working a mini "dummy fiddler" on one side of the stage, while a horribly macabre larger dummy - operated by two figures veiled in black - played on the other. The concert closed with Pete Cooper, Roger Wilson and Joe Townsend, joined by the "Celtic grunge" Ashley MacIsaac, stamping the boards for a Highland fling.

Pitting Anderson's curious tales against "the Gogmagogs Gigagain" at the Bridewell Theatre the following night - presented as part of the City of London Festival - contrasted what seemed like works in progress with genuine finished artistry. Lucy Bailey directed seven young string players in a dozen or so brilliant "music and movement" sketches, starting in darkness with performers and instruments heaped on the floor, then gradually "Getting Up" (Said Murad's title) for joyful "Greetings" (also by Murad). Jane Gardner's The Wildlife trilogy featured illuminated bows imitating tropical fish, extraordinary "monsters" with instruments as heads and a ghostly "Night Choir". There was a hilarious Cable Street Blues by Mike Westbrook where the septet reacted - physically as well as musically - to the suggestive flickerings on an imagined film screen; and then, a little later, John Tavener held us captive with his mystically distended Petra. It was miracle enough that the Gogmagogs could play their instruments from contorted positions, but that their movements, gestures, facial expressions, group timing and, most crucially, musical skills were so expertly balanced - all, plus much, much more - marked them as exceptional artists. "Gigagain" included some of the most entertaining music theatre I've seen in years.

Meltdown continues at the Royal Festival Hall, London SE1 to 5 July (0171- 960 4242)