The Study of Counterpoint:

Species:

I. Note Against Note
Rules:
  1. From on perfect consonance to another perfect consonance, one must proceed in contrary or oblique motion.
  2. From a perfect consonance to an imperfect consonance one may proceed in any of the three motions.
  3. From an imperfect consonance to a perfect consonance one must proceed in contrary or oblique motion.
  4. From one imperfect consonance to another imperfect consonance one may proceed in any of the three motions.

Notes: Must keep the Cantus Firmus in the same mode, especially important if writing counterpoint below the Cantus Firmus. If mode is Dorian, starting note of CF is D, counterpoint below the CF must begin on D to maintain the mode.
Reason for rule moving from imperfect consonance to perfect consonance by contrary or oblique only: By diminution (breaking of longer notes and intervals into short, step-wise motion), one would create two perfect fifths in a row if moving in direct motion.
Always avoid tritones (mi against fa is the devil in musica.) Also to be avoided in stepwise motion, although less strict when reached by two voices in stepwise motion.


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II.
Same rules as first species of counterpoint, except that there are two notes of counterpoint to each one note of Cantus Firmus.
CF is in lower voice, end line in a fifth followed by a major sixth. If CF is in upper voice, fifth followed by minor third. In general, avoid tritones that are in close proximity.
First half note must be consonant, second (on the up beat) can be dissonant only if it moves stepwise. If moving by a skip, must be consonant.
Skip of a third cannot come in between two fifths or two octaves. Most of the time if one substitutes a fourth, fifth, or sixth, it will work. Larger interval causes the ear to "forget".
IDEA: Think about the intervals on the downbeat of each measure and then "connect" them.
One can use a half rest instead of the first note in the counterpoint
If parts have been led too close together, one may use the interval of a minor sixth or an octave jump




2.5. Ternary
Three notes counterpoint to each one note CF. Same rules except middle note can be dissonant only, and still only stepwise. First and third must be consonant. If there are any skips in the three, all three must be consonant.

III. Four notes against each one CF note (quarters against whole notes).
First must be consonant, second may be dissonant, third must be consonant, fourth may be dissonant only if the fifth (first note of the next measure) is consonant (three notes in stepwise motion in the 3rd, 4th, and 5th notes).
If second and fourth are consonant, third can be dissonant. This, in actuality, is simply a diminution of the skip of a third.
Allowed to have a skip after the second note of a 7th if descending, after a 4th if ascending (pg. 51, 52)
Allowed to use a quarter rest in place of the first note.
Final measure: if CF is in lower part, four ascending notes to the tonic or a 9,8,6,7,8 pattern should be used
if CF is in upper part, 7,5,6,7,8 pattern
Avoid sequences! Don't write what the ear "expects" to hear (for instance, rising steps starting at D, F, and A. Instead, possibly use rising steps at D and F, then use skips of fourths from the A to break the sequence. Breaking sequences is GOOD!)




IV. Ligature / Syncopation

Two half notes set against a whole note. Each half note tied to another half note of the same tone, first of a tone must occur on an upbeat, second on a downbeat.
Note on the upbeat must always be consonant.
Consonant ligature if both half notes are consonant, dissonant ligature if first is consonant, second is dissonant.
Dissonance can occur on the downbeat now, must receive resolution from following consonance
Dissonances should resolve descending stepwise to the next consonance (9th to an 8th, 7th to a 6th, 4th to a 3rd, 2nd to a 1st)
Not permissible to proceed from a unison to the second, or an octave to a ninth, because it would cause parallel unisons or octaves. This does not apply to fifths.
If CF is in the bottom, cannot resolve a seventh to an octave. Resolve 2nd to a 3rd, 4th to a 5th, 9th to a 10th
If CF is in lower voice, in next to last measure seventh resolves to a sixth.
If CF is in upper voice, conclude with a second resolving to a third and then a unison.



V. Florid Counterpoint

Combination of all preceding forms of counterpoint. Take care to write a singable melody line.
Try to make use of oblique motion or syncopation in approaching downbeats of measures.
Advice: If two quarters are used at the beginning of a measure followed by a longer ton (ligature or half note), should be followed by shorter notes to make sure it doesn't feel like the melody is lagging.

Next moves into more voices in the counterpoint, going to go back and create examples of all of these first.