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:
- make all the note values twice as long
- make all the note values half as long
- change the time signature from simple to compound (or the other way round).
We have already learned how to do the first two transformations – see Rewriting Rhythms (Grade 3 ABRSM).
At Grade 4, you are likely to see the new time signatures for this grade included.
Remember that doubling the note values means halving the lower number in the time signature:
- 6/8 will become 6/4, 4/4 will become 4/2 and 9/16 will become 9/8, for example.
Halving the note values means doubling the lower number in the time signature:
- 2/4 will become 2/8, 12/8 will become 12/16 and 9/4 will become 9/8, for example.
Changing from Simple to Compound
When changing from a simple to a compound time signature (or vice versa), it is essential to keep the number of beats per bar the same.
- Simple duple time signatures become compound duple.
- Simple triple time signatures become compound triple.
- Simple quadruple time signatures become compound quadruple.
Change the note value which is used for one beat by adding a dot (to make compound time) or removing a dot (to make simple time).
- Simple duple 2/4 = 2 crotchets (quarter notes) per bar >>> compound duple 6/8 = 2 dotted crotchets (dotted quarter notes) per bar.
- Compound triple time 9/16 = 3 dotted quavers (dotted 8ths) per bar >>> simple triple time 3/8 = 3 quavers (8ths) per bar.
Simple to compound: top number x3 and lower number x2.
Compound to simple: top number ÷3 and lower number ÷2.
Here is an example. Let’s transform this bar into compound time:
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.
Any 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).
Any beats which are divided into three with a triplet sign, don’t need any number added (because we already expect them to be in threes in compound time).
Other notes can simply have a dot added. (However, we don’t normally use a double dotted minim (double dotted half note) in 9/8 time – we use tied notes for a full bar).
Changing from Compound to Simple
To change from compound to simple, reverse the process.
Let’s change this compound time melody which is in 12/8. 12/8 has four dotted crotchet (dotted quarter note) beats.
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 (8th notes) grouped in 3s become triplets (“3” added).
Rewriting Exercises
Hover your mouse over the questions (tap on mobiles) to reveal the answers.
1. Rewrite the following in compound time but without changing the rhythmic effect. Include the new time signature.
a.
b.
2. Rewrite the following in simple time but without changing the rhythmic effect. Include the new time signature.
a.
b.
3. Rewrite the following using notes of half the value. Include the new time signature.
a.
b.
4. Rewrite the following using notes of twice the value. Include the new time signature.
a.
b.
