Just as you use letter names as a shorthand method to identify the frequencies of pitch, there are shorthand ways to group beats into sections that make the musical composition more coherent and easier to follow. In musical notation, the grouping of beats is accomplished by the bar line, which separates the staff into measures. A double bar line indicates the end of a section or the end of the piece. A special double bar line with two dots in front of it is called a repeat sign, instructing the musician to go back to the beginning of the section and play it again.
FIGURE 6-1: Bar lines and measures
Each measure (also called a bar) breaks down the hundreds or thousands of beats in a piece of music and divides them into groups of usually three or four beats. Composers occasionally write music with more than four beats to a measure (or less than three), but four beats is by far the most common division and is often referred to as common time. Composers also use three beats per measure extensively, mostly in waltz music. Music with three beats per measure is often called waltz time.
Strong and Weak Beats
Can you tell if a piece of music is divided into measures of three or four beats just by listening to it? Most music has subtle, and sometimes not so subtle clues as to the grouping of the beats. In common time, the first and third beats of the measure are usually the strongest. Beats two and four are usually weaker. In waltz time, beat one is usually the strongest with beats two and three weaker. Does that mean that the notes that land on the first beat are louder in every measure? Not at all. Loudness may be one factor in sensing the strong and weak beats, but not the only one. The way the musical phrasing is constructed and performed may emphasize the stronger beats. Changing the instrumentation slightly on the different beats is also effective (think of a drum set with the kick drum playing on beat one and three with the snare playing on beats two and four).
Listen to Tracks 7 and 8. These examples demonstrate the grouping of beats. See if you can tell just by listening how many beats to a measure there should be for each piece. The correct answers appear at the end of this chapter.
Although the beat is created by sound (in this case musical notes), the beat is not the notes themselves but rather the underlying timing pulse induced in the perception of the listener. There does not need to be a note played on every beat in order to feel the pulse of the music.