It's always been a balm to the envious that, no matter how good their albums, Fridge couldn't cut it live. On record, this trio of precocious, barely-in-their-20s lads from south London experiment with instrumental music in a manner that is graceful, subtle and thoughtful, qualities which they imprudently abandoned when on stage in favour of a clunking rock noise without any distinguishing character. Of course you don't want each track to be faithfully reproduced live, but you don't want the music bludgeoned beyond recognition either.

So it was thrilling at the start of this show when it seemed that Fridge had finally found themselves - that is, found something more in tune with their artful recorded selves - on stage. It wasn't just that they initially left aside the loud guitars in favour of tinkling with samplers, it was the entire event. The venue is more usually home to string quartets and jazz soloists. Instead of a support band, DJ Trevor Jackson span dark electronica. Lazy Eye accompanied the band with mesmerising club visuals. As an alternative to the average men-hunched-behind-equipment-in-a-sweaty- dive show, it was bliss.

And the music was startling. Ark piled heavyweight synth riffs and a bold bassline onto its rustling percussion, building to a breathless crescendo. A tugging bass melody in Aphelion unpinned spiralling keyboards. In Harmonics, a gorgeous sample of percussive strings danced between the left and right speakers while a snowy cymbal shimmered underneath. This was spell-binding work, like Tortoise at their least abstruse, or Aphex Twin when he's being melodic and not just confrontational.

If only it had lasted. Even as a conventional bass-guitar-drums trio, Fridge can produce work that is involving, if lacking excitement: Curdle might be basic pop with a verse-chorus structure, but its waltz timing and light touch gave it an impish, breezy feel. But give these boys a guitar and eventually they'll start indulging in banal rock thrashing. The closing tracks, 2X81 and EH4800, had their interesting moments when the guitar was scraped instead of played, to produce a jittery, crackling sound, and when the bass was played instead of battered, to conjure up a molten melody - but both songs soon descended into a boring cacophony.

The relentless ending was all the more disappointing for the gleaming elegance of the beginning. But there's no denying that Fridge have improved heaps on their previous performances: they'll make a sterling live act in no time.