What is the purpose of time signatures in music?

Time signatures play a crucial role in defining the rhythmic structure of a piece of music. They specify how many beats are contained in each measure (or bar) and what note value is considered one beat. For instance, a time signature of 4/4 indicates that there are four beats in each measure and that the quarter note receives one beat. This foundational aspect of music allows musicians to understand how to group rhythms and accents, leading to a coherent interpretation of the piece.

While other elements such as tempo changes and key signatures are essential to music, they serve different functions. Tempo dictates the speed of the piece, and key signatures identify the tonal center or scale being used. Instrumentation, on the other hand, refers to the specific instruments utilized in a composition, which is unrelated to the concept of rhythm conveyed by time signatures. Thus, the correct answer clearly highlights the role of time signatures in establishing the framework for rhythm and measure in music.