Close harmony in the context of Voice leading

Barbershop vocal harmony 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.

Barbershop music is generally performed by either a barbershop quartet, a group of four typically male singers with one on each vocal part, or a barbershop chorus, which closely resembles a choir with the notable exception of the genre of music.

The Andrews Sisters were an American close harmony singing group of the swing and boogie-woogie eras. The group consisted of three sisters: contralto LaVerne Sophia Andrews (1911–1967), soprano Maxene Anglyn Andrews (1916–1995), and mezzo-soprano Patricia Marie Andrews (1918–2013). The sisters have sold an estimated 80 million records. Their 1941 hit "Boogie Woogie Bugle Boy" can be considered an early example of jump blues. Other songs closely associated with the Andrews Sisters include their first major hit, "Bei Mir Bist Du Schön (Means That You're Grand)" (1937), "Beer Barrel Polka (Roll Out the Barrel)" (1939), "Beat Me Daddy, Eight to the Bar" (1940), "Don't Sit Under the Apple Tree (with Anyone Else but Me)" (1942), and "Rum and Coca-Cola" (1945), which helped introduce American audiences to calypso.

The Andrews Sisters' harmonies and songs are still influential today and have been copied and recorded by entertainers such as Patti Page, Bette Midler, Christina Aguilera, The Pointer Sisters, Pentatonix, and others. The group was among the inaugural inductees to the Vocal Group Hall of Fame upon its opening in 1998. Writing for Bloomberg, Mark Schoifet said the sisters became the most popular female vocal group of the first half of the 20th century. They are still widely acclaimed today for their famous close harmonies. They were inducted into the Minnesota Rock/Country Hall of Fame in May 2006.