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In the third species, four quarter-notes of counterpoint are set against each whole-note of the c.f. (except as specified below).

1. The intervallic requirements for the beginning are the same as those of the first and second species.
2. The first bar of the counterpoint may contain either four quarter-notes or a quarter-rest followed by three quarter-notes.

Main Body

3. What was said about the linear requirements for the added voice in the second species applies to the added voice in the third species as well.
4. The first quarter-note of each bar must be consonant with the c.f.
5. Any of the remaining quarter-notes may be either consonant or dissonant with the c.f. Any quarter-note that is dissonant must be an instance of (a) the passing tone already familiar from the second species; (b) the neighboring tone, which enters by step and continues by step in the opposite direction; or (c) either of two special formations discussed below in rule 6. The neighboring tone makes its first appearance here in the third species. Examples:



6. The third species recognizes as legitimate, in addition, two special formations involving dissonance. These are (a) the double neighbor and (b) the nota cambiata. The nota cambiata is a formation consisting of five quarter-notes beginning with either the first or the third quarter of the bar and having the following properties: (1) the second quarter enters by step and is dissonant; (2) the second quarter continues in the same direction by a third-leap to the third quarter, which must be consonant; and (3) the fourth and fifth quarters (the latter of which must be consonant) move by step in the opposite direction. Examples:



7. A perfect consonance on the first quarter of the bar may be approached only by contrary motion. No parallel succession of perfect consonances may be defined by the respective intervals at the third quarter of a given bar and the first quarter of the following bar. Examples:



8. The unison may occur anywhere in the bar except on the first quarter.
9. The quarter-note voice may not repeat a tone, either within the bar or across the bar line.

Ending (Cadence)

10. The requirements for the final bar of the counterpoint are the same as those of the first and second species.
11. The penultimate tone of the counterpoint must be scale degree 7 if the c.f. has scale degree 2, and (vice-versa) scale degree 2 if the c.f. has scale degree 7.