Traditional fugues have distinct melodic lines, each contributing to the composition's contrapuntal texture and interaction with its main subject.
The subject is the fundamental musical theme, recurring in different keys and undergoing transformations while maintaining its core identity.
The answer imitates the subject in a different voice, with two types: real and tonal, mirroring the intervals and melodic shape.
The countersubject, a secondary theme, provides harmonic and rhythmic contrast to the main subject.