Complete Encyclopaedia of Music/B/Bar
Bar, or BARS. A bar is a line drawn through the staff at right angles to the staff it-self, for the purpose of dividing the notes into equal measures of time. By the aid of the bar, an orchestra or band, however numerous, is regulated and held together. It is by the aid of the bar, also, that the composer figures to us the correspondence of the parts of his score.
Every musical piece is divided into equal portions of time, called measures. These are ascertained by straight lines, called bars, drawn down the staff. All the notes, therefore, contained between two bars, constitute one measure.
In common language, the word bar is used improperly for measure. It is so used in this work, because the use of it has become very common. The word score probably originated from the bar, which, in its first use, was drawn through all the parts, as it should be still, if a piece of music be in partition or partitura. The first introduction of bars took place about the middle of the seventeenth century. Bars always denote strokes drawn perpendicularly across the lines of a piece of music, including between each two a certain quantity or measure of time, which is various as the time is triple or common. In common time, between each two bars is included the measure of four crotchets ; in triple time, three crotchets. Their principal use is to regulate the beating or measure of a musical time in a concert. There is also a thick bar used in music at the end of strains and movements, called the double bar.