The Barbershop Harmony Society, legally and historically named the Society for the Preservation and Encouragement of Barber Shop Quartet Singing in America, Inc. (SPEBSQSA), is the first of several organizations to promote and preserve barbershop music as an art form. Founded by Owen C. Cash and Rupert I. Hall in Tulsa, Oklahoma in 1938, the organization quickly grew, promoting barbershop harmony among men of all ages. As of 2014, just under 23,000 men in the United States and Canada were members of this organization whose focus is on a cappella music. The international headquarters was in Kenosha, Wisconsin for fifty years before moving to Nashville, Tennessee in 2007. In June 2018, the society announced it would allow women to join as full members.

Barbershop vocal harmony, as codified during the barbershop revival era (1930s–present), is a style of a cappella close harmony, or unaccompanied vocal music, characterized by consonant four-part chords for every melody note in a primarily homorhythmic texture. Each of the four parts has its own role: generally, the lead sings the melody, the tenor harmonizes above the melody, the bass sings the lowest harmonizing notes, and the baritone completes the chord, usually below the lead. The melody is not usually sung by the tenor or baritone, except for an infrequent note or two to avoid awkward voice leading, in tags or codas, or when some appropriate embellishment can be created. One characteristic feature of barbershop harmony is the use of what is known as "snakes" and "swipes". This is when a chord is altered by a change in one or more non-melodic voices. Occasional passages may be sung by fewer than four voice parts.