Grade Three Music Theory - Lesson 6: Time Signatures
A time signature is made up of two numbers, one written above the other. It’s written only at the beginning of a piece of music, or within the music if the time signature changes in the middle of a piece. (It’s not written on every new line, unlike the clef and key signature).
The top number tells you how many beats to count in each bar.
The bottom number tells you what type of note to count.
Bottom number 4=crotchet beat
Bottom number 8=quaver beat
Bottom number 2=minim beat.
So 4/4 tells you that there are four crotchet beats in each bar.
Simple and Compound
Up till now you have only learnt about simple time signatures. (Perhaps you didn’t think they were very “simple” though!)
A simple time signature is one where
- the main beat is divided into two
- the main beat is not a dotted note
- the top number in the time signature is 2, 3 or 4
- the bottom number tells you what type of note is used for the main beat
For example, in 4/4 the main beat is a crotchet. If we want to divide the crotchet, we split it into two quavers:
In 3/2, the main beat is a minim. We can split it into two crotchets:
And in 3/8, the main beat is a quaver. We can split it into two semiquavers:
A compound time signature is one where
- the main beat is divided into three
- the main beat is always a dotted note
- the top number is 6, 9 or 12
- the bottom number shows you the division of the beat, not the main beat.
Here are the three compound time signatures you need to know for grade three theory:
The bottom number 8 tells us to count quavers, the top number tells us there should be 6 in a bar. The main beat is not quavers – the main beat is divided into three quavers.
Three quavers = one dotted crotchet.
Therefore the main beat in any /8 time is the dotted crotchet.
The quavers should always (whatever the time signature) be beamed to show what the main beat is:
9 quavers per bar.
Dotted crotchet main beat, divided into three quavers:
12 quavers per bar, each dotted crotchet main beat divided into three quavers:
Remember! An undotted note is always split into two. A dotted note is always split into three.
Duple, Triple and Quadruple Time
All the time signatures that we’ve learnt so far can be described as duple, triple or quadruple.
These words refer to the number of main beats per bar.
In simple time, it’s very easy to work out – just look at the top number. 2=duple, 3=triple and 4=quadruple.
- 2/2 and 2/4 are in duple time
- 3/2, 3/4 and 3/8 are in triple time
- 4/2 and 4/4 are in quadruple time
In compound time, you need to count the number of main beats, or you can divide the top number by 3.
- 6/8 is duple time (2 dotted crotchets per bar)
- 9/8 is triple time (3 dotted crotchets per bar)
- 12/8 is quadruple time (4 dotted crotchets per bar)
Here’s all that information summarised in a table: