Long, unfurling tracks; huge stacks of gear; music like that of no other group; trailblazing live gigs based on improvisation. This is the legacy of Tangerine Dream, the legendary German group piloted by Edgar Froese, whose impact on music, and electronic music in particular, has been profound. Formed in the Summer of Love, and at the beginning a group of rock musicians who liked to improvise, they went on to record and release a series of ground-breaking...