Eric Clapton wrote "Layla" about his love for Pattie Harrison, who was married to George Harrison at the time. He eventually married Pattie, and managed to stay friends with George.
Bruno Mars' "Just The Way You Are" was originally written with Cee-Lo Green in mind, but the Gnarls Barkley singer didn't feel it was right for him.
The game Lana Del Rey sings about in "Video Games" is World of Warcraft - her ex used to play it all the time.
Train wrote the 2011 song "Brand New Book" for the TV show The Biggest Loser - part of the song was used in the opening credits.
Zayn's "Pillowtalk" reached #1 on the Hot 100, something his former One Direction bandmates never achieved.
"Stop Your Sobbing" was first recorded by The Kinks in 1964. It became the Pretenders first single 15 years later, leading to a relationship between Ray Davies and Chrissie Hynde.
Fagen talks about how the Steely Dan songwriting strategy has changed over the years, and explains why you don't hear many covers of their songs.
A song he wrote and recorded from "sheer spiritual inspiration," Allen's didn't think "Southern Nights" had hit potential until Glen Campbell took it to #1 two years later.
The longtime Eagle talks about soaring back to his solo career, and what he learned about songwriting in the group.
How Bing Crosby, Les Paul, a US Army Signal Corps Officer, and the Nazis helped shape rock and Roll.
The Def Leppard frontman talks about their "lamentable" hit he never thought of as a single, and why he's juiced by his Mott The Hoople cover band.