The British Association of Barbershop Singers:
BABS is a registered charity with the aim of promoting music education and the understanding of singing harmony in the barbershop style.
Barbershop harmony is a style of unaccompanied vocal music characterised by consonant four-part chords for every melody note in a primarily homorhythmic (the same word sounds at the same time) texture. The melody is consistently sung by the lead (second tenor), with the tenor (first tenor) harmonising above the melody, the bass singing the lowest harmonising notes, and the baritone completing the chord. Occasional brief passages may be sung by fewer than four voice parts.
Barbershop music features songs with understandable lyrics and easily singable melodies, whose tones clearly define a tonal centre and imply major and minor and barbershop (dominant and secondary dominant) seventh chords that often resolve around the circle of fifths, while also making use of other resolutions. Barbershop music also features a balanced and symmetrical form, and a standard meter. The basic song and its harmonisation are embellished by the arranger to provide appropriate support of the song's theme and to close the song effectively.
Barbershop singers adjust pitches to achieve perfectly tuned chords (instead of tempered tuning like the piano) in just intonation while remaining true to the established tonal centre. Artistic singing in the barbershop style exhibits a fullness or expansion of sound, precise intonation, a high degree of vocal skill, and a high level of unity and consistency within the ensemble. Ideally, these elements are natural, not manufactured, and free from apparent effort.
The performance of barbershop music uses appropriate musical and visual methods to convey the theme of the song and provide the audience with an emotionally satisfying and entertaining experience. Barbershop singers traditionally do not hold sheet music. The musical and visual delivery is from the heart, believable, and sensitive to the song and its arrangement throughout. The most stylistic performance artistically melds together the musical and visual aspects to create and sustain the illusions suggested by the music.
Barbershop can be performed in quartets as well as choirs, and can be found all over the world in male, female, and mixed ensembles.