First species counterpoint adds a contrapuntal line (a second voice) to an existing melody, or cantus firmus. For every note in the cantus firmus there will be a note in the second voice. Before diving into the rules, it is useful to go over some general principles of first species counterpoint.
Know the four types of motion between voices – oblique, parallel, contrary, and similar.
Each voice/line is equally good as an independent melody. This principle of equality of voices fundamentally defines species counterpoint.
The climax of each line should be at a different place, or of a different type. Independent climaxes help to achieve independence of musical line.
Each phrase starts with either a PU, P5, or P8 and ends on either a PU or P8. Starting and ending on perfect consonances gives maximum stability to the beginning and ends of phrases. Perfect intervals are used sparingly in the middle phrases.
Rules of First Species Counterpoint
Only consonant intervals between voices are used (PU/8, P5, M/m3 and compounds). This level of counterpoint is the simplest combination of voices. Dissonances require special handling (additional rules), which comes later. Note that the P4 is a dissonant interval, as are all augmented and diminished intervals.
Do not use the PU except at the beginning or end of a phrase. The perfect unison will eliminate the perception of two voices, and also creates the feeling of closure.
Perfect intervals should be approached ONLY by contrary or oblique motion. Perfect consonances really stand out in comparison to M/m intervals, and improper motion leading to them can thwart the independence of the two voices. The only exception to this rule involves “horn fifths,” which involve a descending 3rd to a 5th, or an ascending 6th to a 5th. In each case, the top voice moves by step.
Parallel and Consecutive PU/5/8s are always incorrect. Again, the starkness of perfect intervals eliminates the feeling of two independent voices.
Voices should not cross or overlap. Crossing and overlaps create aural confusion about the lines.
- voice crossing: at a given point, a lower voice has a note above a higher note, or vice versa.
- voice overlap: a higher voice is on a lower pitch than the lower voice’s immediately preceding pitch, or vice versa.
No more than three parallel 3rds or 6ths in succession. Again, too many parallel imperfect consonances work against the independence of voices.