countersubject

A countersubject is a melodic line in polyphonic music, typically a fugue, that accompanies the subject as it appears in one or more other voices. It is an independent musical idea that provides counterpoint to the subject, often continuing across episodes and reappearances of the subject.

In a fugue, the countersubject usually emerges in a voice that has already presented the countersubject or in the voice that accompanies the subject’s entry. The line is crafted to coexist with the subject according to counterpoint rules, aiming to avoid dissonance on strong beats and to maintain consonant intervals with the subject at its appearances. The result is a continuous conversation between the subject and the countersubject, contributing to the work’s unity and texture.

Countersubjects can be fixed or recur in multiple entries, sometimes appearing in both tonality and related keys. They may be inverted, transposed, or varied, but their identity as a recurring accompanying line helps listeners recognize the contrapuntal relationship with the subject.

In music analysis, a countersubject is identified by tracing a melodic line that consistently accompanies the subject across different entries and episodes. While the term can describe any accompanying melody, in strict counterpoint it refers to a line that regularly accompanies the subject, maintaining independence while harmonically coordinating with it.

See also: fugue, subject, counterpoint, exposition.