A cappella

Group or solo singing without instrumental sound

Music performed a cappella, less commonly spelled a capella in English, is music performed by a singer or a singing group without instrumental accompaniment. The term a cappella was originally intended to differentiate between Renaissance polyphony and Baroque concertato musical styles. In the 19th century, a renewed interest in Renaissance polyphony, coupled with an ignorance of the fact that vocal parts were often doubled by instrumentalists, led to the term coming to mean unaccompanied vocal music. The term is also used, rarely, as a synonym for alla breve.

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