Counterpoint is the mediation of two or more musical lines into a meaningful and pleasing whole. In first-species counterpoint, we not only write a smooth melody that has its own integrity of shape, variety, and goal-directed motion, but we also write a second melody that contains these traits. Further, and most importantly, we combine these melodies to create a whole texture that is smooth, exhibits variety and goal-oriented motion, and in which these melodies both maintain their independence and fuse together into consonant simultaneities (the general term for two or more notes sounding at the same time).

In first species counterpoint, we begin with a cantus firmus (new or existing) and compose a single new line—called the counterpoint—above or below the cantus firmus. That new line contains one note for every note in the cantus: both the cantus firmus and the counterpoint will be all whole notes. Thus, first species is sometimes called one-against-one or 1:1 counterpoint.

The counterpoint line

In general, the counterpoint should follow the principles of writing a good cantus firmus. There are some minor differences, to be discussed below, but generally a first-species counterpoint should consist of two cantus-firmus-quality lines.

Beginning a first-species counterpoint

To exemplify goal-oriented motion, the first-species exercise should begin and end with the most stable of sonorities: perfect consonances. Thus, when writing a counterpoint above a cantus firmus, the first note of the counterpoint should be do or sol (a P1, P5, or P8 above the cantus).

When writing a counterpoint below a cantus firmus, the first note of the counterpoint must always be do (P1 or P8 below the cantus). (Beginning on sol would create a dissonant fourth; beginning on fa would create a P5 but confuse listeners about the tonal context, since fa–do at the beginning of a piece is easily misheard as do–sol.)

Ending a first-species counterpoint

The final note of the counterpoint must always be do (P1 or P8 above/below the cantus).

To approach this ending smoothly, with variety, and with strong goal orientation, always approach the final interval by contrary stepwise motion. If the cantus ends re–do, the counterpoint's final two pitches should be ti–do. If the cantus ends ti–do, the counterpoint's final two pitches should be re–do. Thus the penultimate bar will either be a minor third or a major sixth between the two lines. This is the case for both major and minor keys.

Independence of the lines

Like the cantus firmus, the counterpoint should have a single climax. To maintain the independence of the lines and the smoothness of the entire passage (so no one moment is hyper-emphasized by a double climax), these climaxes should not coincide.

A single repeat/tie in the counterpoint is allowed, but try to avoid repeating at all. This promotes variety in the exercise, since there are so few notes to begin with.

Avoid voice crossing, where the upper voice is temporarily lower than the lower voice, and vice versa. Voice crossings diminish the independence of the lines and make them more difficult to distinguish by ear.

Avoid voice overlap, where one voice leaps past the previous note of the other voice. For example, if the upper part sings an E4, the lower part cannot sing an F4 in the following bar. This also helps maintain the independence of the lines.

Intervals and motion

The interval between the cantus and counterpoint at any moment should not exceed a perfect twelfth (octave plus fifth). In general, try to keep the two lines within an octave where possible, and only exceed a tenth in "emergencies," and only briefly (one or two notes). When the voices are too far apart, tonal fusion is diminished. Further, it can diminish performability, which though not an essential principle of human cognition is an important consideration for composers, and it has a direct effect on the smoothness, melodic integrity, and tonal fusion of what listeners hear during a performance.

In general, all harmonic consonances are allowed. However, unisons should only be used for first and last intervals. Unisons are very stable, and serve best as goals rather than mid points. They also diminish the independence of the lines.

Imperfect consonances are preferable to perfect consonances for all intervals other than the first and last dyads, in order to heighten the sense of arrival at the end, and to promote a sense of motion towards that arrival. In all cases, aim for a variety of harmonic intervals over the course of the exercise.

Never, ever, ever use two perfect consonances of the same size in a row: P5–P5 or P8–P8. This includes both simple and compound intervals. For example, P5–P12 is considered the same as P5–P5. (Two different perfect consonances in a row, such as P8–P5, is allowed, however, but try to follow every perfect consonance with an imperfect consonance if possible.) These "parallel fifths and octaves" significantly promote tonal fusion over melodic independence at the same time that the consecutive stable sonorities arrest both the variety and the motion of the exercise. Thus, they are far from ideal, and to be avoided in species counterpoint.

Vary the types of motion between successive intervals (parallel, similar, contrary, oblique). Try to use all types of motion (except, perhaps, oblique motion), but prefer contrary motion where possible. It is best for preserving the independence of the lines, in addition to variety.

Because similar and parallel motion diminish variety and melodic independence, their use should be mediated by other factors:

• Do not use more than three of the same imperfect consonance type in a row (e.g., three thirds in a row).
• Never move into a perfect consonance by similar motion (this is called direct or hidden octaves). This draws too much attention to an interval which already stands out of the texture.
• Avoid combining similar motion with leaps, especially large ones.

Demonstration

In the following video, I illustrate the process of composing a first-species counterpoint. This video provides new information about the compositional process, as well as concrete examples of the above rules and principles.

Practice

Before composing a first-species exercise from scratch, try the following practice exercises. Each has one or two errors. Try to find the error(s), and recompose the exercise to create a well formed exercise. (Note: the alto-clef part is the cantus firmus. Only change the counterpoint line.) Be sure to listen to and perform the exercises, both as they are written, and as you make changes. Your ear may already be able to direct you to errors. If not, use the principles outlined above one-by-one to search for errors. Once you identify an error, be sure to listen several times, singing along with one line or the other, to train your ear to recognize the problem.

Minor key practice, counterpoint above

Major key practice, counterpoint below