Some sample questions from this category:
* In this former Beatles's first number one hit as a solo artist, a legendary piano player and solo artist is providing the backing vocals. Who is this?
* This famous guitar player performed a solo on one of the King of Pop's number one hits. Who's the guitar player?
* This raspy-voiced crooner had his "other half" of that time providing some sexy French comments in the background of his biggest number one hit. Who was sounding sexy in the background?
* On this former member of the Kingston Trio's solo single, this member of Fleetwood Mac can be heard in the background singing, "There's people out there turning music into gold, into gold."
* On Elton John's first release of his single, "Don't Let The Sun Go Down On Me", a couple members of the Beach Boys provided backing vocals along with a not-yet famous half of a duo. Who was this then unknown?