How Measures Work in Music

Organizing Rhythm in Notation

Musical measure in sheet music.
An empty measure containing a whole rest. Image © Brandy Kraemer

A measure is the section of a ​musical staff that comes between two barlines. Each measure satisfies the specified time signature o f the staff. For example, a song written in 4/4 time will hold four quarter note beats per measure. A song written in 3/4 time will hold three quarter note beats in each measure. A measure can also be referred to as a "bar," or sometimes in written directives in common musical languages as the Italian misura, the French mesure or the German Takt.

How the Measure Developed in Music Notation

Music bars and barlines didn't always exist in music notation. Some of the earliest uses of barlines, which create measures, were in keyboard music in the 15th and 16th centuries. Although barlines create metered measures today, that wasn't the case back then. Sometimes the barlines were used to simply divide sections of the music for better readability. In the late 16th century the methods began to change. Composers started using barlines to create measures in ensemble music, which would make it much easier for the ensemble to find their places when playing together. By the time barlines were used to make every measure the same length it was already the mid-17th century, and time signatures were used to give the bars equality. 

Notation Rules in Measures

In a measure, any accidental that is added to a note that is not part of the piece's key signature, such as a sharp, flat or natural, will be automatically canceled in the following measure.

An exception to this rule is if the accidental note is carried over to the next measure with a tie. The accidental only needs to be written on the first note that it affects within the measure, and it continues to alter each note throughout the measure without the added notation. 

For example, if you're playing a piece of music written in G Major, there will be one sharp — F-sharp — in the key signature.

Let's say the composer wanted to add a C-sharp to a passage of four measures. The first measure of the passage might have three Cs written in the measure. However, the composer only needed to add a sharp to the very first C of the measure, and the following two Cs will remain sharp as well. But we had four measures in this passage, didn't we? Well, as soon as the barline appears between the first and second measure the C-sharp is automatically canceled for the next measure, which makes the C in the following measure a C-natural. In this case, another sharp must be used for the C in the new measure, and the pattern begins all over again. 

This concept also applies to naturals written in a measure; notes in the following measure will not be naturalized unless specified again with a new natural sign. So again using the example of a piece written in G Major, if the composer wishes to create an F-natural in the measure, a natural sign must be used with the F in each measure of the piece since the key signature naturally contains an F-sharp. 

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Kraemer, Brandy. "How Measures Work in Music." ThoughtCo, Sep. 4, 2017, Kraemer, Brandy. (2017, September 4). How Measures Work in Music. Retrieved from Kraemer, Brandy. "How Measures Work in Music." ThoughtCo. (accessed November 18, 2017).