Tom Tom Crew, E4 Udderbelly, London

Time was, circus acts only ever performed under canvas. How things have changed. Australia's Tom Tom Crew are currently to be found on the south bank of the Thames, performing inside an upside-down inflatable purple cow.

Once inside the belly of the beast, however, you won't find anything very extraordinary in their acrobatics, given that the bar has been set so stratospherically high by Cirque du Soleil. They backflip, they tumble (in the controlled sense, mostly), they ricochet off teeterboards, and they do some risky-looking pogo-ing on sprung calipers, but they wouldn't win any medals for it. It's all been done bigger and better.

What Tom Tom Crew lack in fine polish is partly compensated by chummy sex appeal. Every man Jack of them (or should that be Bruce?) could be the love interest in Neighbours. All have great pecs, good teeth, neat tattoos and wear their jeans so that you can read the logos on their underpants.

The intimacy of the venue means that not only does every seat command a premium view, but the kinetic energy of the act communicates through vibration: you literally feel the landings and take-offs, and smell the sweat, if not the fear.

What's more galvanising is the framework: Ben Walsh is an exciting Kodo-style drummer, but he's an even more talented MC, ramping up the tempo with repeated appeals to the crowd that, in that singularly Australian way, turn imperatives into questions, as in: "We need some energy, people(?)." Without his high-octane charm, this might well have the opposite effect.

The live music is the real star of this show. The dexterity of DJ Sampology at his turntables impresses more than any amount of aerial business, enhanced by screens which offer a bird's eye view of his flying hands, alternating with amusing sampled visuals.

There is more unexpected comedy when Walsh drops his macho drummer stance and sings a disarmingly sweet song self-accompanied on electric omnichord – "a piece of Japanese plug-in plastic crap circa 1981" he found in an Adelaide junk shop. In Walsh's hands, the instrument takes on an affecting beauty, its sound something between Appalachian harp and celeste.

But if the omnichord is the evening's solo musical discovery, beatboxer Tom Thum is its full orchestra. Ah, beatboxing, that's where people mimic drum-kits, isn't it? That's what I thought before I heard Thum: a mere boy with scruffy hair and wearing an old T-shirt who, microphone pressed close to mouth, disappears into an alternate universe of Tibetan monks, Dizzy Gillespie's trumpet, didgeridoo, a scratched vinyl record of Fauré's "Pavane" on the cello, and a full set of DJ turntables, outdoing the "real" DJ at a stroke.

He also does a mean few bars of Michael Jackson's "Thriller", simultaneously laying down the vocal over an impression of several instrumental tracks, all generated on the spot. What's the betting he'll be expanding that segment of his act for the next few weeks. Thum is truly phenomenal: just view the other guys as the frills.

Jubilee Gardens, London SE1 (0871 663 2585) to 19 Jul; Edinburgh Fringe 6-31 Aug