Fugue is one of the musical compositional techniques that use two or more voices in its construction. While the material used as a basis for the piece’s layout is fixed, the form of a particular fugue is not set in stone. This gives the composer an opportunity to shape the composition according to their needs and desires. First, in the opening section, called exposition, the main theme of the fugue is introduced in the form of subjects and answers.
The subject is the backbone that is often held throughout the composition, with answers in different tones having their own take at the same melody. Answers can be both real, i.e. with an exactly transported subject, or tonal, with changes to their subject for the purpose of a better harmony. The fugue subject is further separated into a head and tail, with the former used to grab attention and the latter to carry the motion in the melody. Episodes are another design feature of some fugues, providing the composition with the downtime between subjects, giving the composition variety and freshness. The composer uses their imagination, tools, and skill to expand on the subject being introduced in the composition, making small changes to its presentation, or changing the arrangement to continue developing the piece.
Such techniques as sequencing, augmentation, fragmentation, and stretto, among others, can be used. The first of these can be used to provide both variation and repetition, which are both crucial for the creation of a musical composition. Other techniques can be used to achieve similar effects, to either adhere to the principles of a musical composition or break them to offer a brash and surprising take. Stretto, for example, can be used to make two sections of a fugue overlap, which adds to the excitement and acceleration of the piece.