"Wild Horses" is a classic Stones song of course, but so is "Brown Sugar". Even more so, "Brown Sugar" is literally a rock and roll overdose, with Ian Stewart playing a mean bar room rock and roll style piano. Sax player Bobby Keys also contributed enormously to the success of the song. His driving sax is inspirational, but Keith Richards created the foundation for the song with his open-G riff.
In his book The True Adventures Of The Rolling Stones author Stanley Booth mentions the frustrations felt by Ian Stewart during the recording of "Brown Sugar". Keith knew nothing about chords and Stu had to wait for Bill Wyman to interpret the right keys for him. Ian Stewart and a rock and roll overdose...hard to imagine, don't you think? Various versions of the song exist, e.g. this one with Eric Clapton on guitar, but the basic track was cut at Muscle Shoals Sound Studios, on December 4, 1969.
Adapted from the following source: Martin Elliott, The Rolling Stones. Complete Recording Sessions 1962-2002, Cherry Red Books, 2002.