Meghan Trainor and her producer Kevin Kadish wrote "All About That Bass" for another artist to record, but after Epic Records boss LA Reid heard Meghan play a demo of the song on a ukulele, he signed her to his label and told her she should sing it.
"Sing" was inspired by a girl that Ed Sheeran met in Las Vegas in the summer of 2013, when "one thing led to another and now she's kissing my mouth."
Kacey Musgraves offered "Follow Your Arrow" to her friend Katy Perry, but Perry thought Musgraves should record the song herself, telling Kacey it seemed "like something that you would totally say."
A perfume called Wonderstruck was named after a line in Taylor Swift's song "Enchanted": "I'm wonderstruck, blushing all the way home."
After 47 visits to the Hot 100, Justin Bieber topped the tally for the first time on September 17, 2015 with "What Do You Mean?"
"Wanna Be Startin' Somethin'" was Michael Jaskson's attack on the tabloid press: "They eat off of you, you're a vegetable."
"Lullaby" singer Shawn Mullins on "Beautiful Wreck," beating the Devil, and his writing credit on the Zac Brown Band song "Toes."
Andrew Farriss on writing with Michael Hutchence, the stories behind "Mystify" and other INXS hits, and his country-flavored debut solo album.
The Winger frontman reveals the Led Zeppelin song he cribbed for "Seventeen," and explains how his passion for orchestra music informs his songwriting.
The Scorpions and UFO guitarist is also a very prolific songwriter - he explains how he writes with his various groups, and why he was so keen to get out of Germany and into England.
Billie Jean, Delilah, Sara, Laura and Sharona - do you know who the girls in the songs really are?
Switchfoot's frontman and main songwriter on what inspires the songs and how he got the freedom to say exactly what he means.