Counterpoint

Counterpoint is a musical device where melodic phrases play on top of each other, causing notes to work against other notes. The term comes from the Latin punctus contra punctum (note against note). A note moves against another note when the interval between the two notes grows or shrinks. Chords may (and often do) develop when more than two parts are involved, but are incidental; this kind of music focuses on individual melodies working together. The composer Johann Sebastian Bach frequently wrote music using counterpoint.

Generally, such music created from the Baroque period on is described as counterpoint, while music created prior to Baroque times is called polyphony. Hence, the composer Josquin Des Prez wrote polyphonic music.

Homophony, by contrast, features music where chords or intervals play out the melody without working the notes against each other. Most popular music written today use homophony as a dominant feature within the music.

The fugue offers perhaps the most complex contrapuntal convention used today in music.

Species Counterpoint

Johann Fux[?] published Gradus ad Parnassum, a work published in 1725 intended to help teach students how to write counterpoint. In this, he describes five species.

In first species counterpoint, a note simply works against another note. The two notes are played simultaneously, and move against each other, also simultaneously. The species is said to be expanded if one of the notes is broken up (but repeated).

In second species counterpoint, two notes work against a longer note. The species is said to be expanded if one of the shorter notes varies in length from the other.

In third species counterpoint, four notes move against a longer note. As with second species, it is expanded if one of the shorter notes vary in length from another.

In fourth species counterpoint, a note is held while changing note move against the holding note, creating a dissonance, followed by the holding note changing to create a subsequent consonance as the changing note holds. Fourth species counterpoint is said to be expanded when the notes vary in length from each other. The technique requires holding a note across the beat, creating syncopation.

In fifth species counterpoint, sometimes called florid counterpoint, the other four species of counterpoint are combined within the melody.