This isn’t the definitive album of the cool jazz era — it is what it claims to be: a document of that era’s birth. The recordings span a couple of years, during which Miles Davis led a nonet that included musicians who would go on to become major icons of 1950s jazz, including trombonist Kai Winding, saxophonist Lee Konitz, and pianist John Lewis. There’s still a fair amount of bop in the group’s sound, but the audacious arrangements and the soloists’ playing style are pointing clearly to new things to come.