How do we know how many beats should be in a single measure of a piece of music? The answer is simple. We use a time signature.
A time signature is a sign that indicates the meter of a composition. In other words, we know how many beats there are in each measure and which note value we will give one beat by simply looking at the time signature.
In this figure, you can see the time signature of 4/4 meter. Time signature consists of two vertically aligned numbers such as the one in this figure. The upper number indicates the number of beats per measure. So in this figure, there are four beats per measure. The lower number indicates the note value that represents one beat. In other words, in which note value we feel the pulse. In this figure, we feel each beat in the value of a quarter note. We can use any note or rest or combinations of them to fill that four beat. So we can use a whole note, or two half notes, or four quarter notes or rests etc. In 2/4 time, each measure contains two beats and each beat can have quarter note value. In 3/4 time, each measure contains three beats and each beat can have quarter note value.
Time signatures also dictate how we group up shorter notes in each measure. For example, if we want to fill a measure in 4/4 time with eighth notes, we group them up four by four.
Different types of meters
There are different types of meters and therefore time signatures. We can classify meters either by the number of beats per measure or by the subdivisions of a beat.
Meters Classified By The Subdivisions Of A Beat
There are two common type of meters classified by the subdivisions of a beat: Simple meter and compound meter.
Simple meter or simple time is a meter in which each beat of a measure divides into two equal parts. This means if a beat has more than one note, those notes always group up. We can see this clearly with eighth notes. Like I said before, in 2/4 meter (or time) each measure contains two beats and each beat are quarter in value. Let’s say there are four eighth notes to represent those beats. In simple time, we group up those four eighth notes two by two.
I need to mention about beams here. When we want to combine successive eighth or shorter notes, we use beams. A beam is a thick horizontal line connecting the tops of the note stems. So when we combine those eighth notes, we no longer use flags. Instead, we use beams. For sixteenth notes, we use two beams, for thirty-second notes we use three beams and so on. As you can see from the figure, in 2/4 time when we use four eighth notes, we group them two (for beat 1) by two (for beat 2). The upper number of the time signature of a simple meter indicates how many groups of notes will be in a measure. In this example with 2/4, there should be two-note groups in a measure to indicate two beats.
The top number of time signatures of a simple meter isn’t divisible by 3 except when it is 3. This is why 3/4 and 3/8 are simple time signatures whereas 6/4 and 6/8 aren’t. They are compound.
Common Examples Of Simple Meters
The upper number of time signatures will be 2, 3, 4 in simple meters. Common simple meters are 2/2, 2/4, 2/8, 3/2, 3/4, 3/8, 4/2 and 4/4.
March and slow music
Polka and March
Waltz, Country and Ballad
Waltz, Minuet, Country Ballad
Popular music, Classical music, Jazz, Country, Bluegrass
There are two symbols that you will encounter frequently that are used for 4/4 and 2/2 times.
We use Common Time instead of 4/4 time signature and we use Alla Breve instead of 2/2 time signature.
Compound meter or compound time is a meter in which each beat of the measure divides into three equal parts. Each beat contains a triple pulse, a dotted note. The upper number of the time signature of compound meters will be 6, 9, 12 or multiples of 3. In 3/4 simple time, we group beats into three groups of two notes. Actually, they are divided into two equal subdivisions. But in 6/8 compound time, we group beats into two groups of three. So they are divided into three equal subdivisions. This is why 3/4 is a simple meter whereas 6/8 is a compound meter.
Common Examples Of Compound Meters
Common examples of compound meters are 6/8, 9/4, 9/8 and 12/8.
Tarantella, Barbarolle, Irish Jig
Progressive Rock, Balkan Music
12-bar Blues, Doo-Wop
There are some meters that do not fit usual simple and compound meter categories. These are called complex or irregular meters. These meters are common in the music of Eastern Europe such as Balkan dances. But in Western popular music, they are mostly used in experimental genres such as Progressive Rock. The upper number of the time signatures of complex meters include 5, 7, 9, 11, 13, 15, 22, 25.
Meters Classified By The Number Of Beats Per Measure
The duple meter is a musical meter into which we divide each measure into two beats or multiples. Most common examples are 2/2, 2/4 and 6/8.
The triple meter is a musical meter into which we divide each measure into three beats or multiples. 3/4, 3/2 and 3/8 are the most common examples.
The quadruple meter is a musical meter into which we divide each measure into four beats. 4/4 is the most common example.
So we can say that 3/8 is a triple simple meter while 6/8 is a triple compound meter. 4/4 is a quadruple simple meter while 2/8 is a duple simple meter.
We usually write time signatures at the beginning of a piece right after the clef symbol and key signature (if there is one). When we see time signatures in the middle of a score after a bar line, it indicates a change of meter. When we change the meter, it applies to all measures unless we change it back.
As you can see from this example, the first two measures of this piece are in 4/4 time. Then it changes into 3/4 time. The third and fourth measures are in 3/4 time.