It's been 40 years since the Bee Gees song 'Too Much Heaven' topped the pop chart

"Too Much Heaven" by the Bee Gees topped the Billboard pop chart 40 years ago today.

It was the band's contribution to the 1979 Music for UNICEF project, which raised money for world hunger programs.

Joseph Brennan, who has meticulously documented all the recordings by the brothers Gibb, describes an extremely elaborate recording process. In addition to borrowing the group Chicago's horn section, "Too Much Heaven" utilizes 27 vocal tracks to create nine layers of three-part harmony.