Polyrhythms explained – what you need to know!

The concept of polyrhythms is fairly easy to grasp, although not necessarily straightforward to execute. In this post, I will explain what polyrhythms are so you can add them to your instrumental practice or enrich your music compositions. All you need is a basic understanding of rhythm subdivision, beat, and meter. So, let’s dive right in!

What is polyrhythm?

Essentially, a polyrhythm is a combination of two or more different rhythms that follow the same basic pulse reference. They are similar to cross-rhythms but subdivided in different ways.

For instance, let’s say you have a 4/4 measure. One rhythmic layer uses the 4-beat reference for that measure, while the second divides the same 4/4 measure into 5 beats. This is commonly referred to as a 5 against 4 or 5:4 polyrhythm. When both rhythms play together, they form an overall rhythmic phrase that is perceived as one.

Normally, one of the rhythmic parts being played is based on an irrational rhythmic subdivision (like using quintuplets) against another that divides the pulse in multiples of two. Although this is not mandatory, you can have a triplet played against a quintuplet (3:5).

A subdivision of 4:8 is not considered a polyrhythm because it results in two 4s, which divide the beat in the same way. In this scenario, we would call it a cross-rhythm since it layers two or more rhythms using the same subdivisions.

Polyrhythm examples

But enough talk—let’s hear how it sounds. The following polyrhythm example is the composite rhythm of three beats against two (3:2):

You can also combine other subdivisions, such as a 5:4 polyrhythm:

Or even have multiple layers of polyrhythms like 5:4:3:

Each will give you a distinct rhythmic feel that you can follow. Apply it to a drum/percussion part or to a melodic/harmonic instrument:

Example of a 4:3 polyrhythm in the percussion. While the main melody and chord changes are based on a quintuplet subdivision, this creates an overall 5:4:3 polyrhythm.

When working with polyrhythms, focus on the overall rhythmic feel and then build from there. This allows you to move beyond the regular polyrhythmic subdivision. While influenced by it, proceed to a more natural rhythmic phrasing spread across the instruments.

What a polyrhythm is not

Although it’s a fairly simple concept, I’ve encountered some misunderstandings and misconceptions about the topic. Here are some clarifications:

• If you have different measure lengths at the same time, then we are working with polymeters. For example, a musical phrase on the piano in a 3/4 meter over the course of 4 measures, while the drums are playing in a 4/4 meter and meeting the piano phrase after 3 measures.
• Syncopation is the technique of accenting up-beats. Polyrhythms can have syncopation due to the layering of different rhythms, resulting in a composite rhythm that can sound syncopated.
• Polyrhythms are not odd time signatures. Although you can write in odd times using polyrhythms, it’s more common to hear them in common time musical contexts, like in 4/4 or 3/4.
• Sometimes the term cross-rhythm is associated with polyrhythms. While the concept is similar, as it implies having two or more complementary rhythms being played simultaneously, they are not quite the same. With polyrhythms, at least one of the rhythmic layers uses a different beat subdivision.

Can polyrhythms be applied to any instrument?

You may have heard this term most commonly used by drummers. However, any instrument can create polyrhythms. The exception is if you are playing solo on a monophonic instrument. If at least a couple of monophonic instruments are playing together, they can create polyrhythms. Examples of instruments where a single musician can play polyrhythms while playing solo include piano, guitar, or drums.

Why are polyrhythms important?

Several studies in music psychology show that musical rhythm can influence the internal bodily rhythm (i.e., increased heart rate). Over time, the body's rhythm adjusts to external stimuli. This suggests how important rhythm can be to our listening experience, and polyrhythms introduce even more freshness and novelty.

They can add depth and unexpectedness to a song, contributing to emotional responses through music. The theory of ebb and flow suggests that arousal and emotional responses can be induced in a listener due to specific features of music. These features violate, delay, or confirm the listener’s expectations about the continuation of the music, in this case, through the use of polyrhythms!

Polyrhythms can be found across all genres of music as they add excitement and spark creativity. The beauty of polyrhythms is that they can sound like complex rhythmic structures using simple patterns. As an instrumentalist or composer, understanding and playing polyrhythms is a skill worth developing, regardless of the genre of music you study.

Other uses for polyrhythms

One awesome effect you can create while playing with polyrhythms is tempo modulation, also referred to as metric modulation. Tempo can be modulated, just as you can modulate to a different tonality. You can increase or decrease the tempo or BPM in a section of the song. In this case, a passage can be perceived as being played slower or faster even when the tempo doesn’t actually change, creating an illusion of a shift to a new tempo. This is called an implied metric modulation.

One way to achieve this is by introducing a different rhythmic subdivision that contrasts with the one you were using before. You can shift the natural or expected accents of rhythmic figure groups to give the impression of metric modulation. In the example below, you will feel the contrast from shifting between sixteenth notes and eighth-note triplets with a shifted accent:

In this example, we are changing the accent of eighth-note triplets to every 4 notes instead of every 3, while maintaining the same basic rhythm.

Implied metric modulations can also be achieved by playing polyrhythms. This device can capture the attention of listeners, add variety, or prepare a modulation to a new tempo:

In this example, I’m using a 5:4 polyrhythm to give the impression of speeding up the tempo. The kick and snare are in a quintuplet subdivision, while the hi-hats are on a four-note per-beat subdivision.

Conclusion

In this post, we’ve established what a polyrhythm is and what it isn’t, to avoid misconceptions that could hinder your musical studies. Hopefully, you can now see the potential and feel inspired to include polyrhythms in your practice and compositions. Use different polyrhythm combinations to create unexpected rhythmic landscapes or to imply metric modulations. This is just the tip of the iceberg regarding what you can do with polyrhythms. Now it’s time to explore!

About the author:

Pedro Murino Almeida is an award-winning composer with the musical project Follow No One, an expert musician, and an experienced music teacher. He maintains a blog called Beyond Music Theory with the aim of providing tools and instruction for beginning to advanced music students and those wishing to learn about music theory, how to use it, and improve their songwriting and music production skills.