Phil Lesh, who has just played two nights in London, represents an extraordinary phenomenon: the rock musician growing old gracefully, hard at his honest work. Once the bass player of the Grateful Dead, a group so far out on the edge of respectability that they were blamed for leading the Rolling Stones astray in the aftermath of the disastrous Altamont festival, he is still playing with ingenuity and imagination in the tradition that he and his cohort half invented and half stumbled on, which turns American folk musics from jazz to Appalachian bluegrass and rock into a glorious and nourishing musical stew. Most of his peers are either dead, retired, or playing in bands that have turned into karaoke cover acts of their very much younger selves. Lesh keeps trying, like Dylan, to make the music fresh and surprising every night and most nights he succeeds triumphantly. So what if he still can’t sing: we’re nonetheless grateful he’s not dead.