In third-species counterpoint, the counterpoint line moves in quarter notes against a cantus firmus in whole notes. This 4:1 rhythmic ratio creates a still greater differentiation between beats than in second species: strong beats (downbeats), moderately strong beats (the third quarter note of each bar), and weak beats (the second and fourth quarter notes of each bar). Third species also introduces the neighbor tone dissonance, and two related figures in which dissonances can participate in leaps.

The counterpoint line

As in first and second species, the counterpoint line should be singable, have a good shape, with a single climax that does not coincide with the climax of the cantus firmus, and primarily stepwise motion (with some small leaps and an occasional large leap for variety). Like second species, a third-species counterpoint should be even more dominated by stepwise motion than in first species, because there are less sticky situations that would require a leap. If the counterpoint must leap, prefer to do so within the bar rather than across the barline. Also like second species, there should usually be one or two secondary climaxes—notes lower than the overall climax that serve as “local” climaxes for portions of the line.

Beginning a third-species counterpoint

Begin a third-species counterpoint above the cantus firmus with do or sol. Begin a third-species counterpoint below the cantus firmus with do. Unisons are permitted for the first and last dyads of the exercise.

A third-species line can begin with four quarter notes in the first bar, or a quarter rest followed by three quarter notes. Regardless of rhythm, the first pitch in the counterpoint should follow the intervallic rules above.

Ending a third-species counterpoint

The final pitch of the counterpoint must always be do, and must be a whole note.

The penultimate note of the counterpoint (the last quarter note of the penultimate bar) should be ti if the cantus is re, and re if the cantus is ti.

Strong beats

Principles for strong beats (downbeats) are generally the same as in second species.

Strong beats are always consonant, and not unisons. Prefer imperfect consonances (thirds and sixths) to perfect consonances (fifths and octaves).

Motion across bar lines (from beat 4 to downbeat) follows the same rules as first species counterpoint.

Progressions from downbeat to downbeat follow principles of second-species counterpoint, with one exception (see below). The following are some examples, but not an exhaustive list:

• No three consecutive bars can begin with the same perfect interval (two in a row are fine).
• No more than three bars in a row should begin with the same imperfect consonance.
• The pitches that begin consecutive downbeats must not make a dissonant melodic interval.

If a downbeat contains a perfect fifth, neither the third or the fourth beat of the previous bar can be a fifth. If a downbeat contains an octave, neither the second, third, or fourth beat of the previous bar can be an octave. Like in second species, the negative effects of parallel fifths and octaves are not mitigated by the addition of a note or two.

Hidden or direct fifths/octaves between successive downbeats are allowed.

Other beats

Beats 2–4 should exhibit a mixture of consonant and dissonant intervals to promote variety. Among consonances, unisons are permitted on weak beats when necessary to make good counterpoint between the lines. Any dissonance must follow the pattern of the dissonant passing tone or the dissonant neighbor tone, explained below. Also explained below are a number of standard patterns for consonant weak beats.

Harmonic dissonances

Generally, dissonances in third species can occur on beat 2, 3, or 4, and should be preceded and followed by stepwise motion (with the exception of the double neighbor and the nota cambiata, explained below). This promotes smoothness, both by keeping the dissonances off of the strongest beat of the bar, and by coupling them with the smoothest melodic motion. If all dissonant notes in the counterpoint follow one of the following models, they should have a pleasing effect. If not, they may sound harsh or unresolved, or will be difficult to sing.

The dissonant passing tone fills in the space of a melodic third via stepwise motion. The notes before and after the passing tone must be consonant with the cantus.

Note that it is possible to have two dissonant passing tones in a row (P4–d5 or d5–P4). As long as these dissonances do not fall on downbeats and the counterpoint moves in stepwise motion in a single direction, there is no negative effect.

The dissonant neighbor tone ornaments a consonant tone by stepping away and stepping back to the original consonance (6–7–6 over the cantus, for example). It is melodically identical to the consonant neighbor tone of second species, with the difference being the harmonic dissonance. Employing it on a weak beat (2 or 4) ensures the greatest smoothness.

The double neighbor occurs when beats 1 and 4 in the counterpoint are the same tone, and beats 2 and 3 include the notes a step higher and a step lower than the original tone. For example, C–D–B–C or C–B–D–C. Both beats 2 and 3 are dissonant, but since both are embellishing the original tone by step, the leap between them does not significantly diminish the smoothness of the line. When using a double neighbor, the direction between beats 3 and 4 should be the same as between beat 4 and the following downbeat. That motion across the barline should also be stepwise. This further maintains smoothness to temper the effect of the dissonances.

The nota cambiata (changing tone) is a five-note figure that outlines a step progression from downbeat to downbeat. It follows one of two patterns:

• down by step – down by third – up by step – up by step
• up by step – up by third – down by step – down by step

The first pattern will result in a step down from downbeat to downbeat, and the second pattern will result in a step up from downbeat to downbeat. For a nota cambiata to be effective, the first, third, and fifth notes must be consonant with the cantus. The second note will be dissonant and will leap to the third tone. However, like the double neighbor, the overall pattern minimizes the negative effect of the leap away from the dissonance. It is surrounded by stepwise motion, the overall progression is a single step, and the dissonant tone and the following downbeat are the same pitch.

Consonances

The counterpoint can move in and out of consonant tones freely by step, as well as by leap from another consonance, with the following considerations:

• All melodic leaps, of course, must be melodic consonances.
• A large leap should be followed by a step in the opposite direction.
• Motion from the fourth beat into the following downbeat should follow the constraints above for motion into strong beats.

Video demonstration

Add trinkets above to have students construct the schemas