John Martyn, who died last week, was impossible to categorise. He was a folk hero, thanks to his acoustic guitar ballads and highly individual treatment of traditional songs and blues, but his improvised playing was influenced by jazz, reggae and trip-hop, while some of his songs in the 80s veered towards mainstream pop. All of which is reflected in this wildly varied, well-packaged collection, first released last year to celebrate his 60th birthday.

There are four CDs and 61 tracks here, including one song from each of his 22 studio albums, along with rarities and out-takes, and more than 30 previously unreleased recordings that range from over extended experimental pieces to patches of sheer brilliance.

The set starts with Fairy Tale Lullaby, an embarrassingly twee story of pixies and goblins that appeared on his first studio album in 1967, and ends with the sturdy Over The Hill, performed at this year's Folk awards, where he was honoured for his lifetime achievement. His output in the intervening 41 years has been inventive and erratic, but one constant has been the strength of his live playing – shown here by his working of favourites such as May You Never, or the rousing, bluesy I'd Rather Be the Devil from the mid-70s.