Monophony is the simplest of musical textures, consisting of a melodic line or part, typically sung by a single singer or a group of singers in unison or played on a single instrument without accompanying harmony or chords or counterpoint. Many traditional, religious and folk songs are monophonic, including Gregorian chants and other forms of plainchant. Monophony contrasts with heterophony, which consists of two singers or instrumentalists performing varied versions of the same melody together, polyphony, which is two or more singers or instrumentalists simultaneously playing independent melodic lines, homophony, which is a melody accompanied by chords, and monody, which is a single melodic line with instrumental accompaniment.