What does a time signature indicate?

A time signature is a crucial aspect of musical notation that provides specific information about the rhythmic structure of a piece. It indicates two primary elements: the number of beats in each measure (or bar) and which note value is considered one beat.

In the context of the provided options, the correct answer highlights that the time signature specifies how many beats are in a measure, such as a common time signature of 4/4, which indicates there are four beats per measure. The bottom number of the time signature indicates which note value represents one beat, with a "4" meaning that a quarter note receives one beat.

Understanding the time signature is fundamental for interpreting how the music should be played in terms of rhythm, as it helps musicians keep a consistent tempo and timing while performing. This is particularly important when collaborating in ensemble settings or adhering to the composer’s intentions.

The other options address different aspects of music but do not accurately reflect the role of a time signature. For instance, while note duration and dynamics are important elements in music, they are not defined by the time signature itself. Similarly, pitch refers to the highness or lowness of a sound, which is unrelated to the rhythmic implications that the time signature provides.