What is a musical piece for a single voice that is part of a larger work called?

A musical piece for a single voice that is part of a larger work is called an aria. Aria is typically featured within an opera or oratorio, where it serves as a showcase for the singer's vocal abilities and artistry. It is characterized by its expressive melody and is often used to convey the emotions and thoughts of the character at a particular moment in the narrative. The emphasis on individual expression and lyrical content distinguishes an aria from other forms of music within the larger work, making it a significant element in vocal compositions.

The other options refer to different musical concepts. A sonata cycle involves the structure of multi-movement works, typically instrumental, rather than a single vocal piece. Word painting is a technique where music reflects the literal meaning of the lyrics, but it does not define a specific type of vocal piece. Melisma refers to the practice of singing several notes on a single syllable, which is a vocal technique rather than a type of composition. Therefore, the term aria accurately captures the essence of a standalone vocal piece embedded within a larger musical framework.