As I shall be using the term, I intend it to apply to the changing forms of sound across time or space. If typologies are systems for classifying sounds according to their various forms or functions, morphology allows us to gather together sounds with similar forms or functions in chronological or geographical sequence in order that variations or evolutionary changes might become clear. Thus morphology gives us the techniques for both depth-boring and cross-sectioning. In other words, we might use the morphological technique to study the evolution of, say, factory whistles—showing how the physical parameters of the sound were altered over time; or we might compare the factory whistle with alternatives employed in different societies for a similar purpose; that would also be a morphological study.

Schafer, Murray R, The Soundscape- Our Sonic E…, loc. 534