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
Barbershop music of the "revivalist" style are related to the desire to produce these ringing chords. Performance is a cappella to prevent the distracting introduction of equal-tempered intonation, and because listening to anything but the other three voices interferes with a performer's ability to tune with the precision required. Barbershop arrangements stress chords and chord progressions that favor "ringing", at the expense of suspended and diminished chords and other harmonic vocabulary of the ragtime and jazz forms. The dominant seventh-type chord is so important to barbershop harmony that it is called the "barbershop seventh". BHS arrangers believe that a song should contain