Definition
The countersubject is the line that accompanies the answer in the voice that has just presented the subject, and that returns together with the subject in the later entries. If the line appears only once it is called free counterpoint; if it returns systematically it is a regular countersubject. This entry is devoted to the technique of writing it.
Requirements
- Double counterpoint at the octave (or at the fifteenth) with the subject: it must work both above and below.
- Rhythmic contrast: where the subject has long note values, the countersubject moves; where the subject runs, the countersubject holds or syncopates.
- Melodic contrast: mainly contrary motion, with the climax at a different point from the subject's.
- Harmony: together with the subject it defines the harmony clearly (often thirds and sixths on strong beats).
- Recognizability: it must have an identity of its own (a rhythm, a chromatic touch, a syncopation), otherwise it is confused with free counterpoint.
Procedure
- Write the answer (not the subject): the countersubject is born against the answer, in the voice that has finished the subject, and must connect to the end of the subject without strange leaps.
- Think of the underlying first species: one note of the countersubject for each strong beat, only thirds, sixths and octaves (fifths would become fourths in the inversion).
- Embellish the line with passing tones, suspensions and neighbor tones, keeping the strong beats of the skeleton.
- Invert: transpose the countersubject an octave lower (or the subject an octave higher) and check every strong beat.
- Also try it with the subject (not only with the answer) and in the keys of the middle entries, including the minor versions.
Table of octave inversion pitfalls
| Original interval | After inversion | Risk |
|---|---|---|
| 3 | 6 | none |
| 6 | 3 | none |
| 8 | 1 (unison) | avoid on strong beats |
| 5 | 4 | dissonance against the bass: use only as a passing interval |
| 4 (prepared) | 5 | the suspended fourth becomes a fifth: the suspension is lost |
| 7–6 (suspension) | 2–3 | good, the suspension remains correct |
| 9–8 | 7–8 | avoid: an exposed octave arises in the inversion |
Multiple countersubjects
- In three- and four-voice fugues there may be two or three countersubjects: the first accompanies the answer, the second enters with the third entry.
- The three elements (subject and two countersubjects) must be in triple counterpoint: every arrangement must work.
- Example: Fugue in C minor BWV 847 (The Well-Tempered Clavier I), in three voices with regular countersubjects; the Fugue in F# minor BWV 883 introduces the two countersubjects later and combines them with the subject in the final part.
Typical mistakes
- A countersubject with the same rhythm as the subject: the two lines merge.
- Using fifths on strong beats: in the inversion they become fourths against the bass.
- A countersubject that is too interesting: it overshadows the subject.
- A countersubject that begins before the subject has finished, without a melodic link.
Modern application
- Pop and rock: a guitar line that works both above and below the vocal melody (double counterpoint at the octave) is extremely useful in bridges, when you want to swap registers.
- Film scores: a theme and a countertheme in double counterpoint can be swapped between cellos and violins in the repetitions, giving variety without writing new music.
- Choirs: a countersubject in long note values on an open vowel, under a syllabic subject, is the clearest way to make the text understood.
Related topics
Fugue: countersubject, codettas and episodes, invertible counterpoint at the octave, triple and quadruple counterpoint, exposition.