Acoustical analyses of people belting out “Jingle Bells,” “Brother John” and a Polish birthday song, “Sto Lat” reveal that most people sing in tune and in time, even without musical training. Moreover, two distinct “phenotypes”, or recognizable forms, of impaired singing exist that are linked to perceptual abilities. Researchers identified two phenotypes of impaired singing: off-pitch singers with perceptional deficits who don’t know they’re landing on the wrong notes, and poor-pitch singers who can tell they’re off and sing anyway.