Music Theory for the 21st-Century Classroom

Section 30.4 Third Species Counterpoint

1. 🔗

   Begin on an octave or unison. Write four quarter notes to each whole note in the cantus firmus except for the final measure.
2. 🔗

   End on a whole note on an octave or unison with the penultimate measure using one of the following formulas:

   1. 🔗

      If the cantus firmus is in the lower voice, the penultimate measure of the upper voice can be:

      1. 🔗

         $\hat{4}$–$\hat{5}$–$\hat{6}$–$\hat{7}$, or
      2. 🔗

         $\hat{2}$–$\hat{1}$–$\hat{6}$–$\hat{7}$ (the cambiata—see 5.b. below)
   2. 🔗

      If the cantus firmus is in the upper part, the penultimate measure of the lower voice is $\hat{7}$–$\hat{5}$–$\hat{6}$–$\hat{7}$.
      
3. 🔗

   Each downbeat should be a consonance.
4. 🔗

   When crossing barlines, apply the following:

   1. 🔗

      “Imperfect” consonances (3rds and 6ths) can be approached in any manner.
   2. 🔗

      “Perfect” consonances (unisons, 5ths, 8ves, 12ths) may only be approached in contrary motion in order to avoid direct 5ths and direct 8ves.
   3. 🔗

      Do not repeat notes across barlines
5. 🔗

   Allowable dissonances:

   1. 🔗

      Passing tones are allowable dissonances (but never on the first beat of the measure).
   2. 🔗

      The cambiata (see the melodic contour in third measure of the example below) is allowed but only with the second note of the measure as the only dissonant interval.
6. 🔗

   Direct 5ths and direct 8ves are not allowed and occur when an 8ve or 5th on a downbeat is approached through similar motion.