Roger reveals the songwriting formula Clive Davis told him, and if "Eight Miles High" is really about drugs.
A selection of songs made to be terrible - some clearly achieved that goal.
A top country songwriter, Barry talks about writing hits for Little Big Town, Tim McGraw and Jason Aldean.
Was "Ring Of Fire" really used to sell hemorrhoid cream?
"Dead Skunk" became a stinker for Loudon when he felt pressure to make another hit - his latest songs deal with mortality, his son Rufus, and picking up poop.
Despite appearances on Carson, Leno and a Pennebaker film, Williams remains a hidden treasure.
When "Last Friday Night (T.G.I.F.)" climbed to #1 on the Hot 100, Katy Perry became the first woman to send five songs from one album to the top of the charts. The four previous chart-toppers from her Teenage Dream set were "California Gurls," "Teenage Dream," "Firework"; and, "E.T."
Glen Hansard and Marketa Irglova starred in the movie Once, which featured their song "Falling Slowly." Bob Dylan liked the song and movie so much he gave them an opening slot on his tour.
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.
Bob Dylan's four handwritten pages containing the original draft of "Like a Rolling Stone" fetched over $2m at Sothebys New York in June 2014 setting a price record for a popular music manuscript.
"I Won't Back Down" is a very personal song for Tom Petty. "I thought it wasn't that good because it was so naked," he said.
Demi Lovato recorded a Spanish version of her song "Skyscraper," but she doesn't speak Spanish. She performed it on a Latin music awards show with help from a teleprompter.