Second Species Guidelines 2:1
Two notes in the counterpoint against one note in the cantus firmus is called second species. On the first beat of each measure, the half note in the counterpoint sounds together with the whole note in the CF. The first note is always a consonance, and the second note, which is unaccented, may be a consonance or a dissonance. A dissonance may only be approached by a step, not a leap. Thus, the only available dissonances are the passing tone or the neighboring tone.
Rules for Second Species (half notes against whole notes, 2:1)
- The first note should be P8ve, P5th, or unison with the CF. It may begin with a rest on the first beat of the CF.
- Write two notes of CP to each note of the CF. The first note on the strong beat must be a consonance.
- The second note may be a consonance or a dissonance. It is possible to leap to or from a consonance by a 3rd, 4th, 5th, 6 th, or 8ve.
- Movement to or from a dissonance must be by step. Only passing tones and an occasional consonant neighbor tone are permitted.
- Approach each new note of the CF with mostly contrary motion, and some similar motion.
- A unison or a P8ve on successive strong beats is not permitted. P5ths on successive strong beats may occur, if there is a 3rd or 6th between them.
- Treat the final cadence as if it were First Species, with a Clausula Vera.
In general, second species is characterized by occasional passing tones on the weak beat. Fux refers to Strong and Weak beats as “Thesis” and “Arsis.”