You don't have to be a sinner to be moved a mile by Take Six. God help anyone, indeed, who was not jolted into a beatific state last night by the celestial voices and exuberant rhythms of the six former divinity students from Alabama University who make up the world's finest a-capella group.

Ultra-deep bass Alvin Chea, baritone David Thomas, tenor Claude McKnight and the high-flying Kibble brothers started out by singing a little gospel together just for fun, but this hip half-dozen also found common ground in jazz, soul and even hip-hop.

Something remarkable, if not miraculous, then happened and their music became the uniquely powerful mixture that continues to transcend music-biz hype.

How special they are was apparent from their stage positioning. Complex six-part harmonies are difficult to produce even around a single microphone, but they managed these feats pitch-perfectly while standing in line across the apron of the stage, each man using his own mike and wearing an earpiece as a miniature foldback speaker.

Since championed by Spike Lee and Quincy Jones, their fame has grown but their religious beliefs remain strong. There's at least one Christianity commercial per concert, and while many a hardbitten Londoner bypasses such messages, everyone seemed happy to wear a little preaching and enjoy the glorious music that resulted.

Straighten Up and Fly Right, an ingenious reworking of an old Nat Cole standard, was followed by an early gospel hit, I Got Life, drastically modernised when Thomas shouted "Remix!" to trigger a sudden change of pace to heavy hip-hop.

Seven Steps to Heaven, a Miles Davis classic, worked surprisingly well, and a nostalgic medley of Stevie Wonder and Michael Jackson delights was also carried off brilliantly. But it was the gospel songs - Wade in the Water, Shall We Gather by the River, and a sensational encore, Mary Don't You Weep - that packed the biggest punch.

Earlier, Saturday's bill-topper, that urbane keyboard superstar Herbie Hancock, found his stylish new group sabotaged by some rock-stadium knob-twiddling on the RFH's mixing decks. Trumpeter Terence Blanchard, guitarist Lionel Loueke and harmonica expert Gregoire Maret tried their best, but the volume of James Genus's bass-guitar and Kendrick Scott's drums drowned all.

No such problems at the Pizza Express club in Dean Street, where New York-based Puerto Rican tenorist David Sanchez put his post-Coltrane salsa across with remarkable sensitivity, aided by a classy group including British double-bass exile Orlando Le Fleming and an economical and tasteful young guitarist from Norway, Lage Lund.

The festival's opening-night vocal party at the Barbican was also a resounding success. Backed by Guy Barker's admirable big-band and string arrangements, singers Carleen Anderson, Madeline Bell, Liane Carroll, Melody Gardot, Nate James, Christine Tobin and Cleveland Watkiss each savoured the spotlight.

Until 23 November (londonjazz festival.org.uk and bbc.co.uk/radio3).