More decades ago than many of us care to admit, a rock and roll album as gorgeous in sound as it was cantankerous in spirit arrived in record stores and on radio charts that could hardly have been less prepared for it. Fleetwood Mac’s Rumours stood along among the Bat Out Of Hells and Cat Scratch Fevers and Saturday Night Fevers. With its blend of voices as miraculous as its personalities were fractious, the era’s signature musical document was as much a mirror of its time as Sgt. Pepper’s Lonely Hearts Club Band had been a decade earlier.