The California native also wrote tunes including "Rodeo" and "The Girl Who Has Everything."
Mischer produced and directed the 1983 TV special on which Michael Jackson introduced his Moonwalk.
Nathan is credited with getting acts like Barenaked Ladies and 3 Doors Down signed.
Ridley pursued her dreams of singing late in life, competing on season 5 of AGT in 2010 at age 58.
The group announced the passing of the "heartbeat" of the band on Monday morning (April 7).
Gang of Four said Allen was home with family when he passed on Saturday (April 5).
Their 2008 album, Welcome to Mali, received a Grammy nomination for best contemporary world music album.
The star was a major teen idol throughout the 1960s.
"Batman Forever" star Kilmer died on Tuesday at 65 from pneumonia.
He was also the first artist to record a future standard written by Burt Bacharach & Hal David.
