Two lines, one piece of music
Counterpoint is the art of combining melodies. Chords answer the question "what notes sound together?" Counterpoint asks a second question: "how does each line get from one chord to the next?" Good counterpoint gives every line its own shape while the lines still fit.
Four ways two lines can move
- Contrary: one goes up, the other goes down. The most independent, and the safest.
- Oblique: one note stays while the other moves. Smooth and gentle.
- Similar: both go the same way, by different amounts.
- Parallel: both go the same way, keeping the same interval. Fine for thirds and sixths, risky for fifths and octaves.
Consonance and dissonance
Between two voices, perfect consonances (unison, fifth, octave) sound open and stable. Imperfect consonances (thirds and sixths) sound warm and full. Everything else is a dissonance: it adds tension and usually moves on to a consonance. Start and end phrases on consonances; use dissonances as passing notes.
The same ideas shape smooth chord changes. See voice leading, and read the Counterpoint Basics program for a step-by-step route.
Frequently asked questions
What is counterpoint?
Writing two or more melodies that sound good together while each stays an interesting line of its own. The word means "note against note". It is the craft behind fugues, canons, hymn harmony and countermelodies.
What are the four kinds of motion?
Parallel (both lines move the same way by the same interval), similar (the same direction but by different amounts), contrary (opposite directions) and oblique (one line holds still while the other moves).
Why are parallel fifths and octaves avoided?
Fifths and octaves are so stable and so closely related that two lines moving in parallel by those intervals fuse into one. The second line stops sounding independent. Parallel thirds and sixths do not have this effect and are widely used.
Which intervals count as consonant?
In two-voice counterpoint the perfect consonances are the unison, fifth and octave, and the imperfect consonances are thirds and sixths. Seconds, sevenths and (between two voices) the fourth and the tritone are dissonant.
Are these rules strict?
They describe one classical style. Rock, pop and jazz break them all the time, and parallel fifths (the "power chord") are a signature sound. Knowing the rule tells you what you gain and lose when you break it.