Augmentation in composition
A melody or series of notes is augmented if the lengths of the notes are prolonged; augmentation is thus the opposite of diminution, where note values are shortened. A melody originally consisting of four eighth notes for example, is augmented if it later appears with four quarter notes instead. This technique is often used in contrapuntal music, as in the “canon by augmentation” (“per augmentationem“), in which the notes in the following voice or voices are longer than those in the leading voice, usually twice the original length. The music of Johann Sebastian Bach provides examples of this application. Other ratios of augmentation, such as 1:3 (tripled note values) and 1:4 (quadrupled note values), are also possible.
Diminution shortens the melody into half the space of the original