"(What's So Funny 'Bout) Peace, Love, and Understanding" was written by Nick Lowe in 1974. The original version with his group Brinsley Schwarz was kind of somber, but Elvis Costello made it a classic with his 1978 uptempo take.
"Livin' La Vida Loca" is a Latin pop landmark, but "la vida loca" are the only Spanish words in the lyric - "mocha" is English.
An unexpected guest vocal: Marianne Faithfull on the Metallica song "The Memory Remains." A star in the '60s, this collaboration helped revive her career.
In the song "God," Tori Amos makes the point that if there's God, there must also be a Goddess because there are no male-only species.
"(Sittin' On) The Dock Of The Bay," released a month after Otis Redding died, was the first song to hit #1 in America after the artist died.
Avril Lavigne's 2011 song "Darlin" was written much earlier; she says it's the second song she ever wrote, composed when she was an unsigned 15-year-old living in Napanee, Ontario. The song reflects those years when she was "trying to figure it all out."
Taylor talks about "The Machine" - the hits, the videos and Clive Davis.
Jon Anderson breaks down the Yes classic "Seen All Good People" and talks about his 1000 Hands album, which features Chick Corea, Rick Derringer, Ian Anderson, and many other luminaries.
The Doobies guitarist and lead singer, Tom wrote the classics "Listen To The Music," "Long Train Runnin'" and "China Grove."
A top New York studio musician, Ralph played guitar on many '60s hits, including "Lightnin' Strikes," "A Lover's Concerto" and "I Am A Rock."
Cain talks about the divine inspirations for "Don't Stop Believin'" and "Faithfully."
Guitarist Tony Iommi on the "Iron Man" riff, the definitive Black Sabbath song, and how Ozzy and Dio compared as songwriters.