countersubject

A countersubject is a secondary melodic line that accompanies the main subject in a fugue. A fugue is a musical composition characterized by the systematic imitation of a principal theme, called the subject, in simultaneously sounding melodic lines, known as counterpoint.12

The concept of counterpoint, where multiple independent melodic lines are combined, has evolved significantly. Early forms, like organum, involved parallel motion of voices. Over time, these lines became more individualized, with different rhythms and melodic contours. In a fugue, if a melodic line consistently accompanies the subject, it is called a countersubject. However, some fugues do not feature a consistent countersubject, relying instead on free counterpoint.32