I vote for The Golden Gate Quartet. Phenomenal harmony and rhythm in gospel music. "Theodora is Dozing" from the Koutev "Music of Bulgaria" recording. Then there's the tradition of "Sacred Harp" singing. Harmony singing has a lot to do with what's appropriate for the style of music. Lambert, Hendricks and Ross would not be appropriate for bluegrass or sea chanteys but their harmonies were great. Next thread should be Great Singers Hall of Fame. :)

Frank Hamilton