Since the upbeat of each measure acts as a resolution of the suspension, it must be consonant with the cantus firmus. The suspended downbeat may be either consonant or dissonant with the cantus firmus. If the suspended downbeat is dissonant with the cantus firmus, it must resolve down by a step.
Above the Cantus Firmus: Below the Cantus Firmus:
- 2 to 1 - 2 to 3
- 4 to 3 - 4 to 5
- 7 to 6 - 9 to 10
- 9 to 8
Works of fourth species will always resolve in a specific way. If the counterpoint resolves to an octave, the penultimate measure will contain a 7th resolving to a 6th in relation to the cantus firmus. If the counterpoint resolves to a unison, the penultimate measure will contain a 2nd resolving to a 3rd in relation to the cantus firmus. The final pitch of the counterpoint must match the rhythm of the cantus firmus (in our case, it will be a whole note).
In cases where continuing the sequence of ties would cause an undesirable compositional result, the sequence can be broken using regular half notes. In such cases, the sequence of tied rhythms should be resumed as soon as possible. Other than these differences that are specific to fourth species all of the past rules we have discussed still apply.
Based on the rules and tips presented in this lesson, you should be prepared to compose your own third species counterpoint exercises. For more guidance, please refer to the end of the accompanying video where I compose an example of first species counterpoint both above and below a cantus firmus. Continued practice will grant you valuable insight into the nature of melodic motion and the way multiple melodies react harmonically.
This Learning Music With Ray video discusses the topic of fourth species counterpoint. In this video I discuss the rules that govern composing a work of fourth species counterpoint. I also provide some helpful tips that will make your experience composing fourth species counterpoint easier. Finally, I compose a line of fourth species counter point both above and below a cantus firmus in order to provide a live demonstration of the principles discussed in the video.