Turning up unlabeled in the United States, virtually nothing is known about the origins of the tapes that make up Fleetwood Mac’s Before the Beginning 1968-1970: Rare Live & Demo Recordings.

What is known is the three discs consist of 37 live tracks and four studio demos that bookend Peter Green’s time with the band, herald the arrival of fellow guitarists Jeremy Spencer and Danny Kirwan and, as always, are anchored by drummer Mick Fleetwood and bassist John McVie.

And although the sound quality is less than stellar, it’s better than it should be given the tapes sat rotting for nearly a half-century. And the song selection is terrific as the band moves through its most-famous material of the era, including “Oh Well (Part 1),” “Albatross” and “The Green Manalishi (With the Two Prong Crown),” and unexpected covers such as “Long Tall Sally” and “Willie and the Hand Jive.”

Despite the appearance of these rock ‘n’ roll numbers, Before the Beginning is strictly a blues album, full of the grimy, 12-bar variety that finds the band culling material from Fleetwood Mac, Mr. Wonderful and Then Play On, the almost-lost-to-history “Instrumental” and standards such as “Have You Ever Loved a Woman,” “Shake Your Money Maker and “I Can’t Hold Out.”

With only a couple of repeats and just a handful of long instrumental jams – which are not the group’s forte – Before the Beginning is surprisingly engaging across most of its more than 3.5 hours of music. Of course, it’s strictly for fans of the blues and unlikely to appeal to traditional Fleetwood Mac fans who consider Lindsey Buckingham and Stevie Nicks to be original members.