Texture refers to the overall layout of a piece of music. It includes:
Polyphonic music consists of several independent melodies that mostly harmonize, but may have different rhythms. Western polyphony is closely linked to the development of counterpoint since the 14th century. Rows (canons) and fugues are always polyphonic.
A piece of music is homophonic if a dominant melody is accompanied by a dependent harmonic accompaniment. Homophony is today the most common form of texture in Western music. It developed since the 17th century, when the chord replaced the interval as the reference of harmony. Most polyphonic forms of choral music and songs (but not canons!), including modern pop music, are homophonic.
Heterophony signifies textures in which melodic variants are not coordinated with each other:
Different themes do not run side by side at the same time, but all instruments make a fundamentally identical tone movement, but they allow themselves significant individual freedoms, one taking its course in simple quarters, the other playing around with all sorts of embellishments, the third dissolving it completely in semiquaver movements, triplets etc., while the sixteenth-notes of the individual instruments are not in closer agreement. In certain main motives then all meet again in unison.1)
Heterophony (formerly also called „impure unison“) occurs mainly in traditional Asian music; especially when two different instruments are playing together.
Alisha Nypaver, Ephraim Schäfli: Musical Texture
Gamelan Gong Wisnuwara: Tabaki
Mauricio Kagel: Heterophonie (1961)