What is barbershop?
Barbershop harmony is a style of unaccompanied vocal music characterized by four-part chords for every melody note. The melody is consistently sung by the lead, with the tenor harmonizing above the melody, the bass singing the lowest harmonizing notes, and the baritone completing the chord.
The melody is not sung by the tenor, baritone or bass except for an infrequent note or two to avoid awkward voice leading, in tags and codas, or when some appropriate embellishing effect can be created. 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 center and imply major and minor chords and Barbershop (dominant and secondary dominant) seventh chords that resolve primarily around the circle of fifths, while making frequent use of other resolutions.
The presentation 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. The musical and visual delivery is from the heart, believable, and sensitive to the song and its arrangement throughout. The most stylistic presentation artistically melds together the musical and visual aspects to create and sustain the illusions suggested by the music.
For a complete history and interesting information on barbershop please visit the Wikipedia article on Barbershop Music.