II.

Imitative Counterpoint

Counterpoint can be imitative or nonimitative. In imitative counterpoint, the various voices share the same melodic patterns (or motives), imitating one another as in a canon. Imitative counterpoint occurs primarily in genres such as the canon or the fugue and is most characteristic of certain historical periods in Western music (chiefly, the 16th through 18th century). In nonimitative counterpoint, each voice has it own motives.

In imitative counterpoint, several techniques are used to produce variety. The second and following voices can enter on the same pitch as the first (as in a round), or they can enter at a higher or lower pitch. The second and following voices can imitate the first voice exactly or can vary its motives. Sometimes the answering voice is much slower than the first (augmentation, that is, use of longer notes) or much faster (diminution, or use of shorter notes). Sometimes the second voice does not wait for the first to complete its motives, but enters early; such overlapping is called stretto. The answering voice can also turn the motives upside down, imitating every ascending interval by a descending interval, and imitating every descending interval by an ascending interval; this practice is called inversion. Example 2, which shows a passage from Fugue in C Minor by J. S. Bach, illustrates some of these techniques.