The years 1969-1972 marked the first of many transitional periods in the storied history of the unrivaled Fleetwood Mac. They were already a popular blues band in 1969 when they released Then Play On, their stellar third studio album. It was Fleetwood Mac's first with guitarist/songwriter Danny Kirwan who would help steer the band through their next three albums Kiln House (1970), Future Games (1971) and Bare Trees (1972), and ultimately their last with founding member Peter Green. Then Play On's powerful mix of blues and rock includes standout tracks like "Rattlesnake Shake," "Searching For Madge" and "Coming Your Way," and although their time together was short-lived, Green and Kirwan's chemistry here is both definitive in its own right and foreshadowing of the band's future pop-rock brilliance.

"There are arguably three “definitive” Fleetwood Mac lineups. One of them is the blues-oriented band of the late '60s which arrayed three guitarists (Green, Spencer, Kirwan) around the rhythm section of Fleetwood and McVie. They are best represented by 1969’s Then Play On, a milestone in progressive blues-rock. After Green’s exodus in mid-70, the remaining members cut the more easygoing, rock and roll-oriented Kiln House. Early in 1971, a born-again Spencer abruptly left the band during a U.S. tour to join the Children of God. The second key configuration found Fleetwood, McVie and Kirwan joined by keyboardist Christine McVie and guitarist Bob Welch, a Southern Californian who became the group's first American member and a harbinger of new directions. This configuration produced a pair of ethereal pop masterpieces, Future Games (1971) and Bare Trees (1972)." - Rock & Roll Hall of Fame