Tom Donahue

As a Top 40 deejay in Philadelphia and San Francisco, “Big Daddy” Tom Donahue opened his show with a self-spoofing line: “I’m here to clean up your face and mess up your mind.” But it was on the FM band in the late 1960s and ’70s that Donahue changed the face—and sound—of radio. Along with a handful of others, Donahue invented free-form rock radio, in which hipster disc jockeys with a broad knowledge of music—usually...