The term "four-part harmony" refers to music written for four voices, or for some other musical medium—four musical instruments or a single keyboard instrument, for example—for which the various

musical parts A part (or voice) generally refers to a single strand or melody or harmony of music within a larger ensemble or a polyphonic musical composition. There are several senses in which the word is often used: * the physical copy of printed or writte ...

can give a different note for each

chord Chord may refer to: * Chord (music), an aggregate of musical pitches sounded simultaneously ** Guitar chord a chord played on a guitar, which has a particular tuning * Chord (geometry), a line segment joining two points on a curve * Chord ( ...

of the music. The four main voices are typically labelled as soprano (or treble and countertenor), alto ( contralto, countertenor or

mezzo Mezzo is the Italian word for "half", "middle" or "medium". It may refer to: Music *Mezzo-soprano or mezzo, a type of classical female singing voice whose range lies between the soprano and the contralto singing voices *Mezzo forte ("medium-loud") ...

tenor A tenor is a type of classical male singing voice whose vocal range lies between the countertenor and baritone voice types. It is the highest male chest voice type. The tenor's vocal range extends up to C5. The low extreme for tenors i ...

, and

bass Bass or Basses may refer to: Fish * Bass (fish), various saltwater and freshwater species Music * Bass (sound), describing low-frequency sound or one of several instruments in the bass range: ** Bass (instrument), including: ** Acoustic bass gui ...

. Because the human voice has a limited range, different voice types are usually not able to sing pitches that lie outside of their specific range. The effort required to perform four-part harmony varies greatly. Pieces written in such a style can be usually executed by a single keyboard player, a group of 4 instruments (or singers), or even a large choir with multiple singers per part.

In European classical music