What is the function of a bar line in music notation?

The function of a bar line in music notation is to mark the boundary between one bar (or measure) and the next. This vertical line is essential for organizing music into manageable sections, allowing musicians to easily read and understand the rhythmic structure of a piece. By clearly delineating bars, performers can keep time and follow the intended rhythm, ensuring that the music is played as composed.

Bar lines help establish the meter of the music, guiding musicians in terms of timing and phrasing as they navigate through the score. Each measure typically contains a set number of beats according to the time signature, and the bar line visually represents this division, aiding in the performance and interpretation of the music.