A friend to fellow UK folk visionary Nick Drake, John Martyn had his own cult of influence, as this two-disc cover set shows. Drawing on dub and other influences, Martyn took folk-blues into dreamy, uncharted territory, anticipating the roots abstractions of Daniel Lanois and others. Contributors Vetiver, Phil Collins, Vashti Bunyan, and the Cure's Robert Smith make for odd bedfellows. But Martyn's songbook — "May You Never," "Stormbringer," the Drake tribute "Solid Air" — is the star. And with the success of Mumford & Sons (who must've been too busy to contribute), this British folk-pop history lesson couldn't be more timely.