The simmering ballad 'Angie' arrives midway through 1973's 'Goats Head Soup,' perhaps the Rolling Stones' most critically polarizing effort.

After a nearly unprecedented run of full-length glory (stretching from 1968's 'Beggars Banquet' to their 1972 masterpiece, 'Exile on Main St.'), The Stones put out one of their moodiest and most difficult albums. But even the band's toughest critics got on-board with 'Angie,' a deeply moving track built on melancholy acoustics, the haunting piano lines of Nicky Hopkins, and -- most importantly -- Mick Jagger's anguished, passionate vocal performance.

Surprisingly, the track was mostly written by Keith Richards as a metaphor for heroin, which he was attempting to quit.

Watch the Rolling Stones Perform 'Angie'