Counterpoint
Overview
Counterpoint is the art of composing separate melodic lines to be played simultaneously. The melodies must adhere to a specific set of rules and harmonic practices developed throughout the Renaissance and Baroque periods by composers such as Palestrina, Bach, and Fux. The melodies must have a sense of structure and melodic direction independently, while functioning properly in unison. This can be thought of as the horizontal and vertical quality of the counterpoint.
Harmony
Contrapuntal composition begins most often with a 'cantus firmus', abbreviated as 'c.f.' and Latin for 'given melody' or 'fixed melody', a melodic line for the counterpoint to be composed against. To compose a line of counterpoint the melody is written either above, or below, the cantus firmus. The quality of the interaction between the two lines at any given point is assessed by the harmonic interval made between each line on the same beat. Or simply put, the space between the notes of each line. This interval is examined from the lower of the two notes upward, and is categorized into one of twelve harmonic intervals. All counterpoint harmony favors consonant intervals over dissonant ones. There are six consonant intervals, and six dissonant ones.
Consonant intervals:
Strong consonances:
- Unison or Octave
- Perfect Fifth
- Major Third
- Major Sixth
Weak consonances:
- Minor Third
- Minor Sixth
Dissonant intervals:
Strong dissonances:
- Minor Second
- Tritone
- Major Seventh
Weak dissonances:
- Major Second
- Perfect Fourth
- Minor Seventh
However these intervals cannot be moved through aimlessly. Perfect fifths and octaves must be approached from contrary motion and there can be no more than two thirds or sixths of any kind played repeatedly.
A note on fourths.
In a modern context the perfect fourth is considered a strong consonance rather than a strong dissonance. As its use, and perception, have shifted over time. In fact, harmony centered around fourths can be incredibly compelling and expressive. However, if you wish to compose in a more modern or jazz context more rules must be learned and altered than just the addition of an interval. Read more about fourths [here]
The severity of how strictly one should adhere to these intervals depends on the style and genre of the counterpoint they are composing. The quality of the harmonic intervals between lines can be thought of as the 'vertical strength' of the piece, as harmony is notated vertically at any given point. There are other harmonic principles for counterpoint composed in a harmonic minor or other modal context; the above rules apply mostly for counterpoint composed in the major modes.
Melody
There are three types of melodic motion for the movement of the voices to be categorized within in contrapuntal pieces:
Similar motion: both voices move upward or downward by either the same or different intervals.
Oblique motion: one of, or both of, the voices remain unmoving, or on the same note, for multiple beats.
Contrary motion: the voices move in opposite directions from one another, either away from, or towards each other.
Contrapuntal composition favors melodic lines that move in contrary motion, and the overall shape of the counterpoint should be contrary to the cantus firmus.
The counterpoint cannot cross melodic paths with the cantus firmus (i.e. the upper voice plays below a given note of the lower voice, or the lower plays above the upper voice).
However, unison between the voices is allowed (i.e. playing the same note).
The caliber of the melody can be thought of as its 'horizontal strength', as a melody unfolds horizontally through the notation.
Counterpoint is categorized into 'species'. There are five species of counterpoint, starting with First Species.