Well, a couple have to sing the harmony -- one a broken tenor, the other a problematic bass - to the tunes about how light bulbs are changed in (Kentucky, Wyoming, Montana, New Jersey, New England, Nebraska, Old Ireland, old Glasgow, Atlanta, Chicago, Burundi, New HAmpshire, San Pedro, Tivoli) by old (Reilly, Mary, Timmy, Billy, Sammy, Saira, Cindy, Corey, Tommy, Johnny, Bobby, Abdul). Adds at least two, plus the mandolin player.

A.