Micachu & The Shapes and London Sinfonietta

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As long as there's been music, there have been musicians who've used their antecedents' work to augment their own. But only the very best create work that stands apart from the confines of their genres, testing boundaries just for the excitement of seeing what would happen when doing something completely untried.

Look, for example, at the vogue of pop and rock acts augmenting their live shows with classical orchestras or choral outfits (Doves and The Streets' sets during the 2009's BBC Electric Proms, to take but one example). While noble attempts to introduce their audiences to a flavour of what could be found by shuffling a few aisles over in HMV, they are overwhelmingly attempts to bring a heightened sense of occasion and emotion to the existing texts. They don't really engage with their contemporaries on any kind of creative level.

There was little chance of this being the case in a collaboration headed by young tyro Mica Levi, a classically-trained, punk-influenced savant and figurehead of discordant pop outfit Micachu & The Shapes. While completing a degree in composition at the Guildhall she was moonlighting as a Grime MC, and the group's debut record, Jewellery, was an underground sensation, mixing all of her disparate musical influences into something thrillingly original yet remarkably commercial. That genres magpie Matthew Herbert produced it speaks volumes.

As part of the South Bank Centre's Ether Festival – itself an opportunity for musicians and artists of all styles to collaborate and bump against each other in a suitably grand setting - Micachu returns to a collaboration between her band and London Sinfonietta, one of the UK's most boundary-pushing classical ensembles. The results, in short, are electrifying. A true collaboration in all senses of the word, the seven-piece string and woodwind group sit alongside the Shapes and their home-made electronic instruments and drums as complete equals in the creative process. In fact, there are times during the 90-minute performance when the young group seem to sit back and watch in hushed awe as their associates gleefully deconstruct their work, blowing into glass bottles or violently plucking the strings of their violins. It is classical music in a sense, but not anything that would be heard at the Proms.

This is the second time the group has played Chopped & Screwed, initially a one-off event that has now morphed into a live record released by Rough Trade. Apparently derived from a fad by mid-'90s Houston rappers to mainline cough syrup before delivering languid beats, resulting in desperate producers fiddling with the tracks, the whole performance has a woozy, sometimes almost soporific feel, which will suddenly judder into something heart-poundingly alive when least expected. For example, State of NY feels like a prelude to something, all vaguely menacing oboes and uneasy one-note woodwind, while Everything is a driven, almost beautiful percussion-led avant-pop piece that Thom Yorke would surely be proud of.

One of the most fascinating things about Micachu's outfit is that her bandmates are as much a part of the action as she is. Drummer Marc Pell at times acts almost as a conductor to the orchestra and multi-instrumentalist Rasia Khan is allowed to produce some of the evening's best moments on the variety of odd instruments laid out in front of her. Levi herself, when not singing in a haunting, often unintelligible wail, stands watching the rest of the group grinning and nodding along. It's indicative of this egalitarianism among the musicians that the last noise we hear is Khan drawing a bow through the air, creating an atonal buzz that feels like a perfect coda to this dense, fascinating evening.

Micachu is a true one-off – a young British performer who glides between what should be completely juxtaposed genres with ease. There are only a handful of British musicians who can – or will - achieve this level of experimental virtuosity, and none this prodigious. On this evidence, wherever she's going next will be even more exciting.