by Margaret Richer
A bar, also known as a measure in some countries, is the space between two vertical lines called bar-lines. Each bar contains a group of beats, the first usually slightly accented. Set off by the bar-lines, the groups of two, three, four or more beats recur consistently throughout the composition. This basic feel or scheme creates the time signature or meter. Time signatures consist of two numbers placed at the beginning of the piece. The top number shows the number of beats (not notes) in each bar. Music written in 2 time has two beats per bar. The emphasis on the first beat gives the feeling of a march. A piece in 3 time, with the accent on the first beat, resembles a waltz.
Bars also function as directions for repetition within a composition. Heavy double lines – a double bar-line drawn vertically through the staff – divide the work into large sections or indicate the end. Dots placed on either side of a double bar mean that some of the music will be repeated. This is called a repeat sign. Sometimes, a piece may begin with a bar containing fewer than the required number of beats stated in the time signature. The notes in the incomplete bar are often called pick-up notes. In this case, the last bar of the piece will also be incomplete. If the beats of the two incomplete bars, the first and the last, are added together, the total should equal the number of beats required per bar given in the time signature.
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