A cappella music can be produced by a single voice or many voices singing in harmony. Traditional a cappella music is sung by church choirs. In modern times, the style has been adopted by musicians in other venues. "A cappella" is often used to refer to barbershop quartets, doo-wop singing groups and some contemporary pop, folk and rock artists. The only requirement for a song to be a cappella is that only voices can produce the music.
"A cappella" is sometimes misspelled as "a capella," "a cappela" or "occapella." In the United States, the two words are sometimes combined to spell "acappella." These are all incorrect spellings of the Latin term. Some people call any music that contains multi-part vocal harmony a cappella, even if there are non-vocal instruments backing up the voices. This is technically not a cappella. Even a drum beat in the background is considered a non-vocal instrument and would disqualify a song from being a cappella.
A cappella dates back to the early days of organized Western religion. Many ancient Jewish, Christian and Muslim ceremonies involved a cappella chants and hymns. Holy men were often the performers of a cappella music. Gregorian chanting is an example of religious a capella music. It became popular in the late 1980s and early 1990s with the release of the album "Chant" by the Benedictine Monks of Santo Domingo de Silos.
There is a long tradition of a cappella singing on American college campuses dating back to the early 20th century. The type of music they sing changes with the times, but the simplicity of the a cappella style remains the same. Collegiate a cappella evolved from barbershop quartets to doo-wop to beat boxing and rap. There are now hundreds of college a cappella groups across the country. Many compete in a cappella contests and festivals, such as the Georgetown Chimes' Cherry Tree Massacre every February in Washington, D.C.
A cappella music continues to make occasional inroads into popular music. Its purity is often seen as a refreshing change from the increasingly complex nature of pop music. In 1988, Bobby McFerrin's a cappella song "Don't Worry, Be Happy" reached No. One on the Billboard Hot 100 chart. Musicians like The Manhattan Transfer, Boyz II Men and Huey Lewis and the News have also popularized a cappella in some of their songs, but are primarily known for their accompanied music. For a musician to sing a cappella, he must have a very strong voice. Some singers show off their vocals by singing a cappella, as did Christina Aguilera in her song "Beautiful."