Barbershop music countertenor, the baritone resembles the Heldentenor or lyric baritone in range and a tenor in tessitura, and the lead generally corresponds to the tenor of classical repertoire, with some singers possessing a tessitura more similar to that of a high baritone. Barbershop singing is performed both by men's and women's groups; the elements of the barbershop style and the names of the voice parts are the same for both. The defining characteristic of the barbershop style is the "ringing" chord, one in which certain overtones of the four voices reinforce each other, sometimes so strongly that the overtone is perceived
Homer's Barbershop Quartet and his sister Lisa notice a picture of their father, Homer, on the cover of an old LP album. Homer explains to his family that he, Principal Skinner, Barney Gumble, and Apu Nahasapeemapetilon recorded a barbershop quartet album in 1985, which catapulted them to national fame. He narrates to his family the story of how the band formed, reached the pinnacle of success, and eventually folded. At the end of the episode, the group reunites to perform a concert on the roof of Moe's Tavern, singing their number-one hit "Baby on Board". Throughout the episode, several references are made to