They may be here as part of a heavyweight jazz festival, but you can't get much closer to pure entertainment than Vocal Sampling, six Cubans famed for being able to recreate a hot Latin orchestra, a trompe l'oreille achieved with voices and mics.

At first sight you might mistake them for a gracefully maturing boy band. But then you realise that there are no hidden backings - what you see is what you hear.

Sometimes they mime the instrument being imitated: Renato Espinosa strums an imaginary tres, while Oscar Jiménez plucks the air in time to his loping bass lines. Next in line is Abel Padrón, an unstoppable human beatbox who imitates a whole percussion section of congas, bongos, timbales, toms, snares and cymbals.

They begin with René Baños's Un Son Pa' Cantar, a brassy showstopper with a touch of Earth Wind and Fire. Vocal Sampling throw everything into the mix - trumpets, trombones, guitars, drum solos - with great elan. Occasional "big band passages" in close harmony make us realise how meticulously arranged each component must be.

The repertoire includes some classy Cuban dance numbers, as well as crowd-pleasers such as Harry Belafonte's Banana Boat Song (which sounds terrific, even for those of us more familiar with the Stan Freberg spoof) and Mi Guantanamera. For the latter, they divide us into trombones and trumpets for some audience participation. This is followed by leader René Pascual's Hendrix/Brian May style solo "guitar", all distortion and effects, with quotes from Whole Lotta Love and Day Tripper.

Then disaster strikes. As Vocal Sampling don long cloaks to begin a dramatic version of Richard Strauss's dancefloor favourite Asi Hablaba Zarathustra, the PA fails noisily. The stage empties for a few confusing minutes until they return, minus cloaks and mics, to sing Tumamina, a South African hymn, a cappella, as an early, very quiet finale. The audience is spellbound by this beautiful, if unexpectedly low-key ending.