Since species counterpoint always starts with a given melody, a cantus firmus, you will only be composing one line.
Your first steps in composing a counterpoint line involve analyzing the cantus firmus (CF).
- Identify the mode of the CF.
- Note the cadence of the CF (does it end ^2 – ^1, or ^7 – ^1).
- Note the climax of the CF (where, and what type).
- Note the shape of the CF (up, down, both).
Your initial compositional decisions will be based on your analysis of the CF.
- Since you cannot cross or overlap voices, or have parallel unisons/octaves, the shape and cadence of the CF determine the cadence of the contrapuntal line.
- A ^2 – ^1 cadence in the CF means that you will have to cadence ^7 – ^1 (usually #^7 – ^1) in the other voice. If the CF is the lower voice, you will have to end an octave higher in the other voice to avoid crossing. If the CF is in the upper voice, you might be able to end on a PU.
- A (#)^7 – ^1 cadence in the CF calls for a ^2 – ^1 cadence in the second line. If the CF is in the lower voice, you might be able to end on a PU. If the CF is in the upper voice, you will end an octave lower.
- Pencil in your cadence first.
- The shape of the CF will determine whether you can start at the unison, or if you must start at the P5 or P8.
- A lower-voice CF that goes upward will require you to start at least a P5 above, and usually a P8 above the lower voice, to avoid problems with voice crossing and overlaps.
- An upper-voice CF that moves downward requires you to start a P8 below.
- In general, I like to start on the unison or octave.
- The shape and climax of the CF guides your decisions about the shape and climax of the second voice.
My guidelines differ slightly from the workbook instructions for D2. After analyzing the CF,
- Pencil in the cadence (last two notes) of the second voice.
- Determine your starting interval and pitch.
- Write the first few starting pitches of the second voice.
- Plot or visualize a general curve/shape for your second voice, noting where a climax would occur.
- Complete the writing of the second voice. Something that can be very helpful is to write on the staff the possible consonant pitches that would fit with the given note of the CF. You can then see your choices and choose from them as your shape dictates.
As you write your second voice you should be notating the intervals on the page (below the second voice). Writing out the intervals will help you avoid breaking some of the first species rules.
When you have completed writing the second voice, you need to check your work.
- First, check that the second line does not violate any of the rules for melodic writing.
- Check for first species errors after checking the melody. If you’ve followed my advice for plotting possible choices and notating intervals used, this step should be pretty easy.
Remember that a lot of compositional decisions are essentially arbitrary. For example, you need to avoid having climaxes at the same point in each line, but deciding exactly where to put the climax of the second line is up to you. If you plot the shape and climax of your second line before writing the whole line, you may find that your climax choice doesn’t work when you try to get there. You can change your mind and move the climax at this point, but that doesn’t mean it was worthless to try and decide where the climax should have happened. Your arbitrary decision gave you a target to try for, and having this target helped guide you in writing pitches. Not having a target or shape means that you have to pick from a larger world of possibilities with each pitch decision. Finding ways to limit the realm of possibilities makes decisions easier to make.