Imogen Heap, Scala, London <!-- none onestar twostar threestar fivestar -->

Fresh from an American tour supporting her album Speak for Yourself, Imogen Heap is playing a one-off show at the Scala in King's Cross. Tonight's concert is sold out to a hugely enthusiastic audience, and for Heap - born in Essex and living in London - it's very much a homecoming.

She starts the set at the piano, wreathed in light. "Just for Now" is a confident, literate pop ballad that sets the tone for the evening. When it's done, she kicks off her shoes and announces that she's going to introduce her band. The "band" in question is her collection of electronic gear (plus an mbira), and she gives us a demonstration of each item. That completed, she launches into "Goodnight and Go" and "The Walk".

Suddenly, the auditorium is full of people holding up their mobile phones, photographing and videoing. Next up is "Let Go", featured in the movie Garden State and originally by the electro-pop duo Frou Frou, which Heap formed with Guy Sigsworth. Tonight, it's stripped down: just her voice and piano. For "Can't Take It in" - this one from The Lion, the Witch and the Wardrobe - Heap is joined by the support act, Zoe Keating, whose cello, fed through a pedalboard and a black box, forms a dense, writhing undercurrent to the song.

The use of exotic sounds to complement her rather mannered singing style is a central part of Heap's performance. It's a tribute to the strength of her material that the effect is one of a well-integrated world of sound; in the hands of a lesser songwriter, the whole edifice could come crashing down in quite a painful manner. There's a real ability to break things up here, to vary pace and texture.

For "Headlock", Heap sets up a funk-like bassline with a tinkling keyboard over the top, her drum machine crashing in on cue.

What makes her work compelling is the way she is able to manipulate such a wide variety of sounds. The single "Hide and Seek" is a genuine highlight, her voice fed through the electronics to form an intense, multi-layered vocal. "Have You Got It in You?" starts with a sound like a medieval hurdy-gurdy, which is joined by a keyboard pattern reminiscent of Steve Reich's Music for Eighteen Musicians, a piece she has quoted as a favourite.

The main set ends with "Good to Be in Love"; as soon as the drum machine kicks in, Heap picks up the mic and moves to the front of the stage, dancing. She's quickly back, and "Daylight Robbery" turns out to be a rock'n'roll song. She feeds her voice through the vocoder again and dances while the electronics crunches and crashes.

Finally, she returns to the piano for "The Moment I Said It", a moment of real emotional depth, her hands occasionally pattering out a rhythm on the top of the instrument. Then there's just a whispered goodnight, and she's gone.

UK tour 26 March to 6 April; www.imogenheap.com