The latest in Columbia/Legacy's Miles Davis Bootlegs series has four discs representing all four nights played by the trumpeter's new electric band as the support for Laura Nyro at the Fillmore East in June 1970. That controversial and brilliant group included Chick Corea and Keith Jarrett (mingling electronic abstractions and wah-wah-guitar effects on keyboards), and the recurring setlist offers revealing glimpses into the real-time evolution of classics like Directions, Bitches Brew and It's About That Time. The group was also hovering between acoustic, standard-song jazz and raw avant-rock, so longtime Davis staples also get fresh treatments. Just hearing It's About That Time variously played with unadorned trumpet simplicity, or amid menagerie synth-sounds and dense drum shuffles, or accompanied by Airto Moreira's windy flute, in successive nightly interpretations, is fascinating. But a funky Willie Nelson (later to appear on the Jack Johnson album), the rousing, choppy Directions, and the magnificent riff of Bitches Brew are just a few of the highlights subjected to continuous reappraisal. It's a chapter in the story of 20th-century music as a whole, not just the minutiae of jazz.