Final answer:
A musical piece known for its polyphonic development of a primary theme is a fugue, characterized by sequential voice entries playing the same thematic material.
Step-by-step explanation:
A piece based on the polyphonic development of a primary melodic idea is called a fugue. A fugue is a complex style of composition where a single theme or subject is introduced by one voice and is imitated by other voices in succession, traditionally in a keyboard or instrumental setting. This form is known for its interweaving lines that create a rich tapestry of sound, showcasing the composer's skill in developing a single melodic idea across multiple parts.
While sonatas and overtures are instrumental pieces with their unique structures and the aria is a vocal solo piece generally found within an opera or oratorio, it is the fugue that is characterized by the polyphonic treatment of one main theme.