In music, counterpoint is the ability to “say” two things at once comprehensibly. The term comes from the Latin punctus contra punctum, i.e., “point against point” or “note against note.” A single part or voice added to another is called “a counterpoint” to that other, but the more common use of the word is that of the combination of simultaneous parts resulting in a coherent texture. In this sense counterpoint is the same as polyphony.
The art of counterpoint developed gradually from the 9th century onward and reached its highest point at the end of the 16th century and beginning of the 17th century. The chief theorist responsible for the formulation of those rules was Josef Fux whose Gradus ad Parnassum of 1725 is a book that still shows its influence in modern textbooks.
The study of strict counterpoint is divided into five categories or species, as they are known. Based on the practice of early composers, a cantus firmus (fixed song), i.e., a short melody, is written by the teacher against which another melody is to be written by the student or several such melodies. It is usually written with one note to a measure (bar).
The species are as follows:
- Species I
The added voice proceeds at the same pace as the cantus firmus, with one note to a measure.
- Species II
The added voice proceeds at twice (or 3 times) the pace of the cantus firmus with two or three notes to a measure.
- Species III
The added voice proceeds at 4 (or 6) times the pace of the cantus firmus with four notes to a measure.
- Species IV
The added voice proceeds (as in Species II) at the rate of two notes to one, two to a measure; but the second note is tied over to the first note of the following measure, i.e., syncopation is introduced.
- Species V
(Sometimes called florid counterpoint.) The added voice employs a mixture of the processes of the other four species and also introduces shorter notes.
In the twentieth century there have been no additions to the study of counterpoint. Most modern music is based on the study of harmony, which grew out of the analysis of counterpoint. Theorists discovered that contrapuntal music functioned vertically as well as horizontally. Even though the predominant study of modern music primarily involves harmony, there are many music theorists who are convinced that the function of harmony and chord progression cannot be properly analyzed with the exclusion of contrapuntal thinking.