The term BAR OF MUSIC is a musical term referring to a MEASURE, which is a unit of time in music. A MEASURE is a section of a piece of music that is divided by bar lines, which are vertical lines that divide the staff into equal parts. Each MEASURE contains a certain number of beats, and each beat is equal in duration. The bar of music is the basic unit of time in music, and it is used to keep track of the rhythm and tempo of a piece of music.