Listen to Paul Simon's unusual solo recording of "The Sound of Silence" from 1965

This unusual, harmony-free version of "The Sound of Silence" first appeared on Paul Simon's 1965 debut solo album, "The Paul Simon Songbook." It was a re-recording of the acoustic version of the song included on Simon & Garfunkel's "Wednesday Morning, 3 AM" that came out the year prior and also was famously featured in the film The Graduate. Following its radio success, the record label added electric guitar, bass, and drums to the track—without Simon & Garfunkel's permission, which apparently the label didn't need—and that version appeared on the Sounds of Silence released in 1966.