Heterophony

In

David Morton describes the texture in Thai music:

Thai music is nonharmonic, melodic, or linear, and as is the case with all musics of this genre, its fundamental organization is horizontal...

Thai music in its horizontal complex is made up of a main melody played simultaneously with variants of it which progress in relatively slower and faster rhythmic units... Individual lines of melody and variants sound in unison or octaves only at specific structural points, and the simultaneity of different pitches does not follow the Western system of organized chord progressions. Between the structural points where the pitches coincide (unison or octaves) each individual line follows the style idiomatic for the instrument playing it. The vertical complex at any given intermediary point follows no set progression; the linear adherence to style regulates. Thus several pitches that often create a highly complex simultaneous structure may occur at any point between the structural pitches. The music "breathes" by contracting to one pitch, then expanding to a wide variety of pitches, then contracting again to another structural pitch, and so on throughout. Though these complexes of pitches between structural points may strike the Western listener as arbitrary and inconsequential, the individual lines are highly consequential and logical linearly. The pattern of pitches occurring at these structural points is the basis of the modal aspect of Thai music.^[3]

He goes on to suggest the term polyphonic stratification, rather than heterophony:

The technique of combining simultaneously one main melody and its variants is often incorrectly described as heterophony: polyphonic stratification seems a more precise description, since each of the 'layers' is not just a close approximation of the main melody, but also has distinct characteristics and a style of its own^[4]

Examples

Heterophony is somewhat rare in

J.S. Bach:

as well as Mozart:

and Mahler:

In the