What does the term 'opus' signify in music?

The term 'opus' in music signifies the chronological number of a composer's works. It is used to catalog or identify the order in which a composer's pieces were published or composed, often as a way to provide context regarding the evolution of their oeuvre. For instance, Beethoven's "Piano Sonata No. 14" is commonly referred to as "Op. 27 No. 2," indicating that it is the second sonata published under his 27th opus. This classification helps performers, scholars, and listeners to identify specific works and understand the compositional timeline of the artist.

This understanding is distinct from concepts like tempo, which refers to the speed of the music, or key signature, which pertains to the tonal center of a piece. The style of the music also encapsulates the aesthetic and genre, which are separate from the chronological numbering provided by the term 'opus'. Thus, the use of 'opus' is specific to the organization of a composer's repertoire over time.