While most bands undergo a number of changes over the course of their careers, few of them experienced a more radical stylistic evolution than Fleetwood Mac. Initially conceived as a hard-edged British blues combo in the late '60s, the band gradually evolved into an incredibly popular and influential pop/rock act over the course of a decade. Originally, guitarists Peter Green and Jeremy Spencer provided the group with their gutsy psychedelic blues-rock sound, then the band moved toward pop/rock with the addition of keyboardist/songwriter Christine McVie. By the mid-'70s, Fleet...