Many of the artists who propelled the popular folk music revival of the early 1960s by mid-decade had traded their acoustic guitars for amplified instruments and created a new genre of pop music that DJs labeled "Folk Rock." This week, My Place program explores the family tree of several of the more prominent 1960s folk rockers, illustrated with memorable recordings by the Rooftop Singers, the Mamas & Papas, the Byrds and others.