Also known as plainsong, plainchant is a monophonic unison chant of Christian liturgies. Originally unaccompanied by musical instruments, many variations of plainchant have developed over the centuries, including Gregorian chant, developed in the 8th century.

Plainchant often uses plainchant notation. The earliest forms of this musical notation outlined the melody without representing specific notes, and over time this developed into a system of notation with 4 stave lines and square notes. Plainchant can be responsorial (developed from recitation of psalms) or antiphonal (developed as pure melody).