Naturally 7, Barbican

Naturally 7 represent the point where close-harmony singing, beatboxing and spookily accurate instrumental imitation meet. The US septet call it "vocal play" - the voice as instrument - and last night they sent dopamine levels soaring in the Barbican. The group conveys the beat-driven swagger of hip hop, the freewheeling improv of jazz and the trenchant emotion of soul, often within the confines of a single song.

Their arrangements, courtesy of MD Roger Thomas, possess such textural imagination and technical finesse that they're able to traverse genres seemingly without artifice.

Part of the pleasure of watching the band live is trying to work out just exactly who's doing what. While bass and drum duties are clearly delineated (the powerhouse rhythm section of Armand “Hops” Hutton and Warren Thomas), identifying who's producing that squiggly synth line, the high soprano wail or any other number of inner parts is no easy task. Their ability to replicate an instrument's particular timbral quality occasionally required you to pick your chin up off the floor, nowhere more so than Polo Cummings's guitar solo in “Wall of Sound”. The attack, the sustain, the vibrato – it's so lifelike it's uncanny (check out the axe solo at 3:19 in the YouTube clip below).

For hardcore jazzers, a medley of Herbie Hancock classics was pure delight

Songs such as their classic take on “In the Air Tonight” - a YouTube phenomenon (five million hits and counting) - and the sumptuous harmonies of “What the World Needs Now” saw the group's gospel roots come strongly to the fore, albeit flavoured with a typically hip-hop twist. With its dramatic lighting and slick choreography – their stagecraft throughout was nonpareil - the biblically themed “Jericho” unfolded almost as a stand-alone mini-drama. Opening with a hypnotically repeating unison vocal riff, swathed in an appropriately cavernous reverb, the sudden blaze of harmonic colour at the first chorus was one of many moments that took the breath away.

For the hardcore jazzers in the audience, a medley of Herbie Hancock classics – the hocketing riffs of “Watermelon Man”, the oft-covered “Chameleon” (featuring that bass line) and Hancock's turntablist smash “Rockit” - was pure delight. But it was the Simon and Garfunkel medley - “Sound of Silence”, “Scarborough Fair” and “April Come She Will” - performed at the front of the stage without mics, that provided the evening's heartstopping, pin-dropping moment.

Ranging from solo vehicles – starting from just bass drum and hi-hat, the "drum" solo veered off into all kinds of polyrhythmic byways incorporating scratching, snatches of vocal and other percussive ear candy – to the full ensemble, the palette of sound that Naturally 7 worked with was extraordinarily large. The group's ability to dramatically alter the textural density in a heartbeat, suddenly flipping the entire might of the septet to a lone voice, was terrifically effective. Whichever way the sound hit you, the arterial force of the music was irresistible.

The London-based Cameroonian singer-songwriter Muntu Valdo opened the evening with a set of songs from his most recent album, The One and the Many. Ranging from the haunting melody of “No Mercy”, subtly reinforced by delicately picked-out guitar lines, to the meticulously constructed vocal harmonies of “Djongo”, Valdo's singular West African blues possessed a warmth and honesty that really connected with the audience.

Watch Naturally 7 performing "Wall of Sound"