The terms duple, triple, and quadruple refer to the number of beats in a measure.




The term simple means that each of these beats can be broken into two notes.




For example, 2/4 time is classified as simple duple.




''Duple'' refers to the two beats per measure.




''Simple'' states that each of these beats can be divided into two notes.




2/2 and 2/8 are also simple duple.




3/4 time is classified as simple triple.




''Triple'' refers to the three beats per measure.




Again, ''simple'' states that each of these beats can be divided into two notes.




3/2 and 3/8 are also simple triple.




4/4 time is classified as simple quadruple due to its four beats which can be divided into two notes.




4/2 and 4/8 are also simple quadruple.




Notice that a time signature in simple meter will always have a 2, 3, or 4 for the top number.




While beats in simple meter are divided into two notes, beats in compound meter are divided into three.




To demonstrate this, we will examine 6/8 time.




The six eighth notes can either be grouped into two beats (compound duple) or three beats (simple triple).




Since the simple triple pattern already belongs to 3/4 time, 6/8 is compound duple.




Notice that each beat in 6/8 is a dotted quarter note. In fact, all compound meters will have some dotted note as its beat.




Any time signature with a 6 on top is compound duple. 6/8 and 6/4 are the most commonly used.




9/8 time is classified as compound triple.




There are three beats (three dotted quarter notes), thus making the meter triple.




Since each beat is made up of three notes, the meter is compound.




Any time signature with a 9 on top is compound triple. Although 9/8 is the most common; 9/2, 9/4, and 9/16 can also be used.




Finally, 12/8 time is classified as compound quadruple.




There are four beats, thus making the meter quadruple.




Since each beat is made up of three notes, the meter is compound.




Any time signature with a 12 on top is compound quadruple. 12/8 and 12/16 are the most commonly used.