What is a defining characteristic of a fugue?

A fugue is a complex and highly structured form of music characterized by the interweaving of multiple melodies, or voices, that chase one another through the use of counterpoint. In a fugue, one voice presents a main theme, known as the subject, which is then imitated and developed by subsequent voices, creating a layered and intricate musical texture. This "musical chase" is essential to the fugue's identity, as it highlights the interplay and thematic development among the different voices.

The elements of improvisation are not defining characteristics of a fugue, as this form relies on pre-composed material. Likewise, a fugue is not restricted to a slow dance rhythm; rather, its tempo can vary widely. Lastly, while solo instruments can be featured, a typical fugue involves multiple voices or parts, reinforcing the idea of thematic interplay rather than focusing on a single instrument. Thus, the defining characteristic of a fugue is its structure involving a musical chase with multiple voices.