What is a short musical idea referred to in composition?

A short musical idea is referred to as a motif in composition. A motif is typically a brief, distinctive musical idea that can be developed and varied throughout a piece, serving as a foundational element for the music's structure.

Motifs are significant because they provide cohesiveness and unity to compositions, allowing composers to explore different variations and transformations while maintaining a recognizable musical thread. Composers often use motifs to create recognizable themes or to evoke specific emotions or atmospheres throughout their works.

In contrast, themes are generally broader musical ideas that may be comprised of multiple motifs and are often the main subject of a piece. Phrases are segments of musical thought that can encompass motifs but may be longer and more developed. Lastly, cadences denote harmonic resolutions and are not focused on the melody itself. Understanding the role of a motif helps clarify the organization and development of musical compositions.