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victoria Williams Music Theory

Victoria Williams

LmusTCL BA Mus (Hons) MISM

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9. Duplets & Rewriting in a New Time Signature

Grade 4 Music Theory Lesson 9: Duplets & Rewriting in a New Time Signature

We have already learnt about triplets in grade 2 music theory. Just to refresh your memory, triplets are used when we want to play three notes in the space where there would normally be two: 


The triplet (circled here) is marked with a "3". Three quavers (eighth notes) take up the same amount of time as two normal ones. 

Triplets are very commonly seen in simple time signatures, when the composer wants to split the main beat into three, instead of two.


Duplets work in a similar way - but instead of writing three notes in place of two, we use a duplet to write two notes in place of three:


This example is in 6/8. Normally the dotted crotchet (quarter note) beat would be divided into three quavers (eighth notes), as in the first bar.

The duplet is used in the second bar, to divide the dotted note into just 2 quavers. It has the effect of making them a little bit slower than the regular quavers.


Click on the "play" button, to hear the duplets being played against a steady quaver (eighth note) beat:


Try singing along, so you get a feel of how the duplets need to be slowed down! 

Duplets are very commonly seen in compound time signatures, when the composer wants to split the main dotted beat into two, instead of three.


Questions about Duplets

In the grade four exam, there will probably be one or two questions which involve duplets or triplets.

  • You might be asked to give the meaning of the symbol - for duplets, write "play 2 notes in the time of 3," and for triplets, write "play 3 notes in the time of 2."
  • You might see duplets or triplets in the composing a rhythm question (see lesson 10).
  • You might be asked to rewrite a bar or two of music, changing it from compound to simple time, or vice versa. This usually involves some triplets and duplets. (Read on for more!)


Rewriting a Rhythm in a New Time Signature

It's possible to change the time signature of a piece of music without changing the rhythmic effect. This means that the rhythm sounds the same.

There are three basic ways of doing this:

  1. make all the note values twice as long
  2. make all the note values half as long
  3. change the time signature from simple to compound (or the other way round).


Let's take an easy 3/4 bar as an example:

simple time bar


1. Make all the note values twice as long.

First let's change the time signature. 3/4 means there are three crotchets (quarter notes) per bar. To make the note values twice as long, we'll need to put three minims (half notes) per bar, so the time signature will become 3/2. (Remember that the bottom number tells you what type of beats to count.) 

Next, we simply write out the same notes, but make each one twice as long. A crotchet becomes a minim, (a quarter note becomes a half note), and so on:

twice as long


2. Make all the note values half as long.

We'll need three quavers (eighth notes) per bar, so the time signature becomes 3/8. 

Each note is re-written using a note half its value. A crotchet becomes a quaver, (a quarter note becomes an eighth note), and so on.

half as long


When we make the notes half as long, we often need to put some beaming in, as in this example. This means you'll also sometimes need to change the stem direction of some notes - we had to change the stem on the C here. It's a good idea to write all the note heads in first, without their stems, and then add the stems and beams at the end.


3a. Change the time signature from simple to compound.

Instead of having three crotchets (quarter notes) per bar, we'll need three dotted crotchet beats per bar. This means the time signature will become 9/8.

To work what the new time signature is, put a dot next to each main beat note, then count up the quavers (eighth notes) or crotchets (quarter notes). For example, if your original melody is in 3/2 (three minims/half notes per bar), change it to 3 dotted minims/half notes per bar. Now add up the crotchets (quarter notes). There are 9, so the time signature will change to 9/4.)


Each beat will become a dotted beat. In the melody we are looking at, the beat is a crotchet (quarter note), so we make these dotted.

Beats which are divided into two will need a duplet symbol added (because in compound time we would expect the beat to be divided into three).

Beats which are divided into three with a triplet sign, don't need anything added (because we already expect them to be in threes in compound time).

as compound time


3b. Change the time signature from compound to simple.

Let's change this compound time melody which is in 12/8. 12/8 has four dotted crotchet (quarter note) beats.

12 8


Change the dotted beats to undotted notes: four undotted crotchet (quarter note) beats = 4/4.

Dotted notes become undotted notes.

Duplets become "normal" (nothing added).

Quavers (eighth notes) become triplets ("3" added).

4 4



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