Is the official 1990s revival upon us? Stereo MCs are not an act who crop up often in 2010 – their blend of acid jazz with funk basslines and vocalist Rob Birch's scattershot raps is distinctly unfashionable. Despite their multiple hits (you recognise more than you'd think), it's as if they've been written out of British dance music history.

On the evidence of tonight, they haven't been forgotten, though. The band never split, but there is the festive air of a long-awaited reformation in the Royal Festival Hall's Clore Ballroom, a curious setting to play host to a crowd of beer-soaked ex-ravers of a certain age on a nostalgia trip. They're not disappointed: Birch looks even more like a scarecrow than he did in 1992, but time hasn't affected his capacity for stage capering or the enthusiasm of his madcap exhortations. Their breakbeat-heavy music may sound dated to those who weren't there, and the constant insistence on "crazy shit" and "crazy funk" is cringeworthy, but they can't be faulted for their populism.

By contrast, the Bays' raison d'être is the four-piece's standing outside the music industry, dealing only in live, improvised electronics. They aim straight for dancefloor madness, though, with big beats and no-nonsense electro riffs. Their ability to extemporise has been honed to the point where their set sounds polished and practised, and they use this to good effect in segueing seamlessly between a wide range of styles. Eclecticism can be tricky, but the Bays succeed by corralling their industrial breakdowns and hip-hop vocal samples into a coherent, singular aesthetic: a collage of familiar sounds arranged in an unfamiliar way. When the Stereo MCs return to share the stage at the end, they too are subsumed into it.