By 1965 Miles Davis had gone through a handful of stages, from the Birth of the Cool nonet's multihued orchestrations to the development of a hard-bop sound keeled on Davis's midregister wooziness and the band's driving backbone in the "first" great quintet (featuring John Coltrane), to the modal freedom of Kind of Blue. So when the solidly established Davis convened a new quintet, known as his "second" great one, and hired youngsters Wayne Shorter, Herbie Hancock, Ron Carter, and Tony Williams, it seemed a skewed move. These six CDs show just how creatively and intelligently skewed the move really was. The material here, which has also been reissued on expanded single CDs of the main full-length original LPs (E.S.P., Miles Smiles, Sorcerer, Nefertiti, Miles in the Sky), is immediately and unceasingly startling. Davis & Co. were quickly discarding their live performance practice of playing loads of standards and were further discarding traditional melodic structures for more rigorous harmonic exercises. Shorter in particular, at times the most prolific composer in the band, was advancing his tunes and his solos in equal proportion. The tunes are increasingly sharp-edged and, with Williams driving the band with a categorical balance of abandon and control, loopily energized. Miles blows with tighter and tighter control of his tone even while the band seems to be finding all kinds of expressive freedoms that easily elongate into lengthier studies. Toward the end of this box, you'll hear the seeds of the Miles that went on to unloose Bitches Brew. Even though the roots of the aggressively electric Miles are in these sessions, there are uncategorizable points of beauty strewn all over the tunes.