Counterpoint is a very general feature of music (especially prominent in much Western music) whereby two or more melodic strands occur simultaneously – in separate voices, either literally or metaphorically (if the music is instrumental).
The term comes from the Latin punctus contra punctum ("note against note"). The adjective shows this Latin source more transparently: contrapuntal. By definition, chords occur when multiple notes sound simultaneously; however, chordal, harmonic, "vertical" features are considered secondary and almost incidental when counterpoint is to the fore. Counterpoint focuses on melodic interaction rather than harmonic effects generated when melodic strands sound together. It was elaborated extensively in the Renaissance period; but composers of the Baroque period brought counterpoint to a kind of culmination; and, broadly and with many exceptions, it may be said that harmony then took over as the predominant organising principle in musical composition. The late Baroque composer Johann Sebastian Bach wrote most of his music exploiting counterpoint, and explicitly and systematically explored the full range of contrapuntal possibilities in such works as the Art of Fugue.
Given the way terminology in music history has evolved, such music created from the Baroque period on is described as contrapuntal, while music from before Baroque times is called polyphony. Hence, the earlier composer Josquin Des Prez wrote polyphonic music.
Homophony, by contrast with polyphony, features music where chords or vertical intervals work with a single melody without much consideration of the melodic character of the added accompanying elements, or of their melodic interactions with the melody they accompany. As suggested above, most popular music written today is predominantly homophonic - governed by considerations of chord and harmony. But these are only strong general tendencies, and there are many qualifications one could add.
The form or compositional genre known as fugue is perhaps the most complex contrapuntal convention. Other examples include the round (familiar in folk traditions) and the canon.
Counterpoint is one of the most essential means, in musical composition, for the generation of musical ironies; a melodic fragment, heard alone, may make a particular impression, but when it is heard simultaneously with other melodic ideas, or combined in unexpected ways with itself, as in canon or fugue, surprising new facets of meaning are revealed. This is a means for bringing about development of a musical idea, revealing it to the listener as conceptually more profound than a mere pleasing melody.
In 1725 Johann Fux published Gradus ad Parnassum, a work intended to help teach students how to write counterpoint, a method for learning to compose. In this, he describes five species.
In first species counterpoint, each note in an added part* (or parts) simply works against one note in the given part (the cantus firmus). Notes in all parts are sounded simultaneously, and move against each other simultaneously. The species is said to be expanded if any of the added notes is broken up (simply repeated).
In second species counterpoint, two notes in the added part (or parts) work against each longer note in the given part. The species is said to be expanded if one of the two shorter notes differs in length from the other.
In third species counterpoint, four (or three) notes move against each longer note in the given part. As with second species, it is expanded if the shorter notes vary in length among themselves.
In fourth species counterpoint, a note is sustained or suspended in an added part while notes move against it in the given part, creating a dissonance, followed by the suspended note then changing (and "catching up") to create a subsequent consonance with the note in the given part as it continues to sound. Fourth species counterpoint is said to be expanded when the added-part notes vary in length from each other. The technique requires chains of notes sustained across the boundaries determined by beat, and so creates syncopation.
In fifth species counterpoint, sometimes called florid counterpoint, the other four species of counterpoint are combined within the added part (or added parts).
It is a common and pedantic misconception that counterpoint is defined by these five species, and therefore anything that does not follow the strict rules of the five species is not counterpoint. This is not true; although much contrapuntal music of the common practice period indeed adheres to the rules, there are exceptions. Fux's book and its concept of "species" was purely a method of teaching counterpoint, not a definitive or rigidly prescriptive set of rules for it.
- (Note: in counterpoint, the parts or individual melodic strands are often called voices, even if the music is thought of as instrumental.)
Since the Renaissance period in European music, most music which is considered contrapuntal has been written in imitative counterpoint. In imitative counterpoint, two or more voices enter at different times, and (especially when entering) each voice repeats some version of the same melodic element. The fantasia, the ricercar, and later, the fugue (the contrapuntal form par excellence) all feature imitative counterpoint, which also frequently appears in choral works such as motets and madrigals. Imitative counterpoint has spawned a number of devices that composers have turned to in order to give their works both mathematical rigor and expressive range. Some of these devices include:
- Inversion: The inverse of a given fragment of melody is the fragment turned upside down – so if the original fragment has a rising major third (see interval), the inverted fragment has a falling major (or perhaps minor) third. (Compare, in twelve tone technique, the inversion of the tone row, which is the so-called prime series turned upside down.) In a completely separate sense, a contrapuntal inversion of melodies being simultaneously sounded by voices is the subsequent switching of the melodies between voices, so that for example an upper-voice melody is now sounded in some lower voice, and vice versa.
- Retrograde refers to the contrapuntal device whereby notes in an imitative voice sound backwards in relation to their order in the original.
- Retrograde inversion is where the imitative voice sounds notes both backwards and upside down.
- Augmentation is when in one of the parts in imitative counterpoint the notes are extended in duration compared to the rate at which they were sounded when introduced.
- Diminution is when in one of the parts in imitative counterpoint the notes are reduced in duration compared to the rate at which they were sounded when introduced.
Dissonant counterpoint was first theorized by Charles Seeger as "at first purely a school-room discipline," consisting of species counterpoint but with all the traditional rules reversed. First species counterpoint is required to be all dissonances, establishing "dissonance, rather than consonance, as the rule," and consonances are "resolved" through a skip, not step. He wrote that "the effect of this discipline" was "one of purification." Other aspects of composition, such as rhythm, could be "dissonated" by applying the same principle (Charles Seeger, "On Dissonant Counterpoint," Modern Music 7, no. 4 (June-July 1930): 25-26).
Seeger was not the first to employ dissonant counterpoint, but was the first to theorize and promote it. Other composers who have used dissonant counterpoint, if not in the exact manner prescribed by Charles Seeger, include Ruth Crawford-Seeger, Carl Ruggles, Dane Rudhyar, and Arnold Schoenberg.