As with the songwriting teams that I wrote about last month, early on writing the music and writing the lyrics were handled separately.  From Wikipedia:  "One of the patterns that the Jagger/Richards collaboration initially followed has been that [Mick] Jagger  wrote most of the lyrics while [Keith] Richards focused on the music.  Jagger discussed this in [a] 1995 interview with [Jann Wenner], whereby he explained how songs like 'Get off of My Cloud', 'As Tears Go By', 'Wild Horses', 'Tumbling Dice', and 'Beast of Burden' were created.  Jagger has also pointed out that this pattern was more prevalent in the early 1960's, while in their later collaborations their roles have overlapped more, with both of them contributing lyrics and music." 

(May 2015)