This is the original version of ‘The Sound of Silence‘ from 1964 from the album ‘Wednesday Morning, 3 AM’: Just Simon’s guitar and the vocals.
After ‘Wednesday Morning, 3 AM‘ flopped, they split up.
Without either of their knowledge, both electric guitars and drums were added and this version of The Sound of Silence became very popular, reaching #1 on the charts in America on New Years Day, 1966.
Because of this, Simon and Garfunkel teamed up again and created three more studio albums, one of which one a Grammy award for album of the year and song of the year (Bridge Over Troubled Water).
Information garnered from YouTube comments, relevant links added. Why? Because I love this song, I will be including in my radio-show one Friday soon on 5KIxFM Kangaroo Island Community Radio. Listen out for it.