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.