Understanding rhythm

Side Note

Note that this article discusses what rhythms are, not how to learn to play them. If you want to learn to play them, see How to practice rhythms.

I want you to stop reading this, and get up and go for a walk. As you are walking, notice how your feet meeting the ground form a consistent pattern? hit, hit, hit....

Now, imagine that you were to play note every time a foot hits the ground, one pitch for your left foot, and a different pitch for your right? It would sound something like this.

This consistent division of time is called 'pulse' or beat, and is the foundation of all rhythms. In fact, it is also how the speed or 'tempo' of music is measured. The number of beats per minute, or BPM.

Beat grouping

Rhythms are frequently organised into fixed numbers of beats, as repeating patterns are one of the things that makes music sound musical. For example, it is very common to find rhythms grouping beats into fours, which sounds like this:

And you'll also hear music that is based on a grouping of 3. If you consider a rhythm like this while walking, counting '1, 2, 3', you'd notice that the first 'hit' of each group happens on a different foot, giving it a swaying feel. The waltz dance uses this, as does the mazurka.

Other groupings like 5 beats, for example the jazz tune 'Take 5' also exist. Essentially, rhythms can be structured around groupings of any number of beats, but groupings of 4 and 3 are the most common.

Time signatures

Such groupings are so common, that rhythms are typically expressed in relation to them. This is called the 'time signature'.

Time signatures are expressed by two numbers, usually placed one above the other, but in text can be written as two numbers with a slash. For example the time signature '4/4' ( read 'four four') means '4 quarter notes', and is one way of expressing a rhythm based on a grouping of 4 beat chunks.

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In a time signature, the top number tells you the number of notes in the group, and the bottom number names a note duration. '4/4' means '4 quarter notes'. Notes of different shapes represent longer or shorter periods of time, in relation to each other:

Side Note

Note that a time signature is not a mathematical fraction, even though it may look like one visually. It is just a way of expressing a grouping.

Within the '4/4' time signature, a quarter note is a quarter of the duration of the group. But how would you represent a rhythm based on a group of 3? This is normally done using the time signature '3/4':

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You may find that this doesn't make sense, as now the quarter note is being used to represent a 3rd of the group's duration.

Functionally, the 'quarter note' is an abstract value used to represent a division of time. A quarter note is a quarter of the duration of a whole note, not a quarter of the duration of the group.

Notes have no inherent time value. The absolute duration of any note can only be known in relation to the value defined as a basis in the time signature.

You can organise note types in a graph like following, with each level going downwards, halving in its duration, and so twice as many of that note type fit in a given period of time. Notice how the quarter note lands in the middle?

Music notes have a recursive structure, where each successive type of note has a duration half that of the previous note type: whole note, half note, quarter note and so on

Using the quarter note as the base reference just gives a good range of freedom to create longer and shorter notes, given the available note types.

Rhythmic figures, and varying note duration

Within a single one of these groups, the lengths of the notes can be varied for interest and expression. Instead of playing a note every beat, the note can be held to span two beats. And the time duration of a single beat can also be subdivided.

An example, using 4/4 time. Note that gaps have been added to allow you to hear the groups separately.

And this is how the same would be written in music notation. 4 quarter notes, 2 half notes, and 8 eighth notes.

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Notes of different lengths can be combined within a single bar to make it sound more interesting.

And this is how you'd notate the same thing in sheet music:

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Just like melodies, rhythms also have 'figures', short patterns which are repeated to form a longer rhythm. Figures don't have to span an entire bar. For example, you may have the following figure:

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And then build a more complex rhythm out of it by repeating it multiple times:

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Realising this is extremely helpful when it comes to learning to play rhythms, as once you know how a particular figure sounds, its easy to read it within a longer rhythm. That point is covered in more detail in How to practice rhythms.

The following example demonstrates a rhythm formed by combining 2 different figures which complement each other.

Rhythms can be formed from pretty arbitrary collections of note durations, as long as they align with the grouping. If you just play notes with random durations the sense of grouping vanishes and the rhythm sounds weird:

Down and up beats

If you were to take the 4 beats of a group in 4/4 and split those in two, the ones that are first are called 'down' beats and the ones in the middle are called 'up' beats. This creates an 'uplifting' feeling somehow.

When a note spans multiple up beats, its called syncopation.

Dotted notes and ties

Adding a dot after a note extends its duration by half its length.


X: 3
M: 4/4
L: 1/4
K: C
C3C

You can also notate notes of different lengths using ties, which joins two notes together into one longer note:


X: 3
M: 4/4
L: 1/4
K: C
C2-CC

Adding two dots extends a notes length by half, and again half.

Rests - not playing anything

Another way that interest can be added to a rhythm is to insert gaps or not play notes.

In music notation, such a 'gap' is called a rest. Rests exist that have equivalent durations for all of the note types, you can also dot them, although it does not make sense to tie rests, given that a rest already means 'do nothing'.

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Triplets

3 notes in the space of 2. Triplets introduce unevean subdivision.

Compound time

In 3/4, you have a beat every note. But what about if you instead wanted to divide each beat into 3? Well you can, and there's nothing difficult about it.

But how would you notate it? One option is to start with a time signature like 1/4, and then notate every bar as a triplet.

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However doing that would get visually cluttered in longer music. Instead, we use a convention called 'compound time'.

In compound time, each bar is considered to be a duration of one or more groups of 3 8th notes, or one or more dotted quarter notes. But there is no way of doing that, as there is no way of notating the value of a dotted quarter note in a time signature.

Instead, the convention is to notate this as '3/8' instead. This represents the same thing as the example above, one beat split into groups of 3:

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Compound time is used whenever you want to create a grouping based on dividing each beat into one or more groups of 3. For example:

  • 3/8 1 group of 3 - used in the French 3-time Bourree
  • 6/8 2 groups of 3 - the quintessential 'jig' found in Irish, Scottish and English folk dance tunes
  • 9/8 3 groups of 3 - the Irish slip jig
  • 12/8 4 groups of 3 - the Irish slide

The relationship between the time signature and beats

The exact relation between beats, and the time signature is not entirely straightforward. In a time signature like 4/4 or 3/4, the number of beats in each measure is defined by the bottom number in the time signature. It also works for a time signature like 2/2, which implies playing something twice as fast, considering two beats per bar.

But then '6/8' compound time implies 6 beats, when as we explored above, there are only 2.

In practice the time signature 'sometimes' tells you the number of beats in the music, but it can be ambiguous. To clarify this ambiguity, you'll often see a metronome mark above the staff, which says that some note duration has some number of beats per minute.

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Using a metronome mark also allows you to change the base reference duration without changing the tempo. Technically the following two are equivalent, although the second looks strange to people familiar with notation:

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Irregular groupings

Rhythmic figures and phrases do not have to align with the bars. Bars may mark a mathmatical division of time and the structure of the music does not have to stick to that.

You can also form rhythms that are based on irregular groupings of notes, for example 3 quarter notes, 3 quarter notes, and 2 quarter notes. Here are a few variations on that. The song 'clocks' by Coldplay uses such a grouping in its introduction.

Closing notes

Here we have explored the structure of rhythms and how they are notated. However, it is important to note that rhythms are not always played exactly as they are written.

Listen to and study the rhythms in the music that you are listening to. If you can, find sheet music for them, and see how different rhythm sounds are written.

Use musescore, which lets you play music and see the notation at the same time, so you can see how it sounds.

If you want to learn how to play rhythms, I recommend learning how they sound first, and then secondly learning how notation represents that sound. See How to practice rhythms.

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And this is how you'd represent those same patterns in music notation.

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