Monophony is a pure voice, nothing extra. The oldest songs of humankind sounded this way: lullabies, work calls, ritual chants.
In the Western tradition the peak of monophony is Gregorian chant, which took shape mainly in the 9th–10th centuries. In Ukrainian culture it is the znamenny chant and ancient folk songs sung a cappella without any accompaniment. Monophony returned in the 20th century — in the works of John Cage, Morton Feldman, and in the minimalist jazz of Keith Jarrett.
Monophony should not be confused with heterophony — an ancient kind of group performance in which everyone sings “the same” melody but with small divergences and ornaments. Historically it was monophony that formed the first stage in the development of music, out of which polyphony and homophony later grew. In the sacred tradition, pure monophony still carries a special significance — from Gregorian chant to the znamenny chant.
