Zayn's "Pillowtalk" reached #1 on the Hot 100, something his former One Direction bandmates never achieved.
KT Tunstall's "Suddenly I See" was inspired by Robert Mapplethorpe's photograph of Patti Smith on the cover of her album Horses.
Neil Young wrote the CSN&Y song "Ohio" about the Kent State Shootings, when the National Guard opened fire on students at Kent State University in Ohio, killing four.
Pink Floyd's "Talkin' Hawkin'" uses a sample of Stephen Hawking's synthesized voice taken from a speech he made for a 1994 British Telecom commercial.
The White Stripes song "We're Going To Be Friends" is very innocent, but Jack White feared it would be interpreted cynically. It wasn't, and was even adapted into a children's book.
Richard Harris, who played Professor Dumbledore in the first two Harry Potter movies, had a hit in 1968 with "MacArthur Park."
U2, Carly Simon, Joanna Newsom, Brian Wilson and Fiona Apple have all gone to Van Dyke Parks to make their songs exceptional.
"25 or 6 to 4" to "Semi-Charmed Life" - see if you can spot the songs that are really about drugs.
Guitarist Tony Iommi on the "Iron Man" riff, the definitive Black Sabbath song, and how Ozzy and Dio compared as songwriters.
Before he was the champ, Ali released an album called I Am The Greatest!, but his musical influence is best heard in the songs he inspired.
He wrote "She Blinded Me With Science" so he could direct a video about a home for deranged scientists.