What is defined as a set of five horizontal lines in music notation?

In music notation, a staff is defined as a set of five horizontal lines and the four spaces between them used to represent musical pitches. Each line and space corresponds to a different note, which allows musicians to read and write music effectively. The staff serves as the foundation for notating rhythm and pitch, and it is further enhanced by the addition of clefs that indicate which notes correspond to which lines and spaces.

The other options represent different elements of music notation. A clef is a symbol placed at the beginning of the staff to indicate the pitch of the notes to be played. A measure is a segment of time defined by a given number of beats, generally marked by vertical lines on the staff. A note indicates a specific pitch and duration within the context of the staff. Understanding the function of the staff is essential, as it is fundamental to reading and interpreting music.