Dark Ducks

Dark Ducks is a male chorus group consisting of:

Takamizawa Hiromu (高見澤宏, born November 9, 1933)
Sasaki Tooru (佐々木行, born February 18, 1932)
Kisou Tetsu (喜早哲, born November 8, 1930)
Tooyama Hajime (遠山一, born Mai 26, 1930)

(Source: AniDB)