In this species (and don't get too excited here) you'll be dealing witha Cantus Firmus
in whole notes combined with a melody in tied half note
- As per usual, the first measure will always begin with a half rest; also as per usual, the first note must be a half note and a 5th or octave of the tonic triad or a unison with the tonic itself. Whee!
- The first half note will be tied to the first half note of the second measure, thus creating a suspension.
- The last measure, once again, must be a whole note in octave or unison with the cantus.
- Every other measure in this species must be comprised of two half notes. The first half note must be a consonant or dissonant suspension. Dissonances must be used whenever possible. The second half note in each measure has to be a chord tone, thus actually finishing off (resolving) the suspension.
- Every dissonant suspension you write has to resolve by descending one scale degree.
- In order to create tension and proper resolution, a dissonant suspension in the next-to-last measure is always desirable.
When the cantus firmus is the bass, here are the dissonant suspensions you can feel free to use:
- The 4th to the 3rd
- 7th to 6th
- 9th to 0ctave
- 6th to 5th (remember all the fun 6/4 rules?)
- 4th to 5th
- 2nd to 3rd
- 5th to 6th
In any relevant case mentioned above, the 6th is always theoretically a dissonance unless it is being resolved to by a 5th, in which case the 5th is the dissonant interval.
- Append to the above set of rules: If your cantus is in the lower voice, never use the 6-5 suspension twice in a row. This would create parallel fifths, and then I'd have to burn you. Also, the resolution of a suspension must not form an octave with the part above it if the cantus is in the upper voice.
- With the cantus in the lower voice, totally avoid unisons.
- Parallel fifths are disallowed unless seperated by an entire measure in the upper part. However, since the cantus is in the lower part here, the final measure may contain a 5th.
- As a last resort you may break your suspensions up with untied half notes to avoid screwing up really badly. Use your second species rules here until you get out of trouble and then continue on the path.