John Martyn, Barbican, London

'Some people keep diaries – I make records," John Martyn once claimed, admitting that his 1980 album Grace And Danger was "probably the most specific piece of autobiography I've written". Coming after his marriage had broken down, Grace and Danger was a cathartic exercise that many found too bleak, among them the boss of Island Records, Chris Blackwell, who declined to issue the album until pressure from Martyn secured its release a year after it was made. Like other very personal, nakedly emotional records, it has developed a reputation as one of the singer's best, and he has come to regard it as his favourite. Last year, it was accorded the double-disc reissue treatment, and now he's performing it in its entirety.

That's overplaying the album's importance. Most fans would vote for Bless the Weather or Solid Air to be re-created live; but then this isn't strictly a re-creation, Martyn being disinclined to leave a song untouched in performance. Over an hour and a half, the songs, and additional favourites, melt together into one elongated folk-jazz flow, punctuated by bouts of indecipherable patter about "despair... divorce... lawsuits" and private jokes.

During the opening "Cooltide" and "Some People Are Crazy", the sound is too foggy: when Martyn's black Les Paul scatters Echoplexed chords over the fretless bass, sax and polite keyboards, the sound oozes together into a miasmic whole, a situation not helped by his warm, slurred vocals.

"'Angeline'!" cries out a punter, met by Martyn's swiftly dismissive "Oh, I don't think so". He and the band plough on with their ersatz Weather Report stylings, the most agreeable of which are those with unsinkable melodies, such as "Sweet Little Mystery" and his cover of The Slickers' reggae classic "Johnny Too Bad", which is stretched into more amorphous jazz-rock.

He performs a solo version of Lonnie Johnson's "Mr Jelly Roll Baker" on acoustic guitar, those huge fists peeling off dizzying licks without moving a millimetre. It's a dazzling demonstration of the virtuosity that established Martyn's reputation four decades ago, but the backing band returns all too soon to see out the set on the crowd-pleasers "May You Never" and "Solid Air".

"Remarkable," he mutters between songs. "Y'know, I used to do this for a living!" He still does, and at his best, it's still remarkable. It's just more carefully concealed these days, which is a pity.

Touring to 25 November (0844 844 0444)