Polyrhythm and rhythmic displacement

Rhythm gets interesting when two patterns pull against each other. A polyrhythm puts two different divisions of time together, such as three against two. Groupings like 3-3-2 lay odd-length groups over a steady 4/4. And displacement takes a phrase you know and starts it at a different point in the bar, so the same notes sound new. All three appear in rock, Latin, African, funk and jazz music.

By the end of this lesson you will be able to:

• Clap and play three against two.
• Strum the 3-3-2 grouping over a 4/4 pulse.
• Displace a short phrase by an eighth note and keep it in time.

Polyrhythm means two different divisions of the same time span happening together. The most common is three against two: in the time of one bar, one part plays three evenly spaced notes and another plays two. Count six fast pulses: the three-part plays on 1, 3 and 5; the two-part on 1 and 4. Together they make a lilting, rocking pattern found in African, Afro-Cuban, classical and jazz music.

The 3-3-2 grouping. Eight eighth notes in a 4/4 bar can be grouped 3 + 3 + 2 instead of 2 + 2 + 2 + 2. Accent the 1st, 4th and 7th eighths (1, the "&" of 2, and 4) and you get one of the most widely used rhythms in popular music: the backbone of a lot of Latin, rock and pop grooves. It pulls against the steady four, which is exactly why it sounds exciting.

Rhythmic displacement takes a phrase and starts it at a different point in the bar: an eighth note later, or a beat later. The notes stay the same, but they fall on different beats, so different notes get accented. Improvisers use it to make a single idea last: repeat it, but shift it.

In all three, one thing stays fixed: the pulse. Your foot and the metronome do not move. Only the pattern on top does.

Three against two on the table.

1. Count "1 2 3 4 5 6" steadily.
2. Tap the left hand on 1, 3, 5. Tap the right hand on 1 and 4.
3. Together, the hands make "both, left, right, left": the rhythm of "pass the gol-den but-ter".
4. Move it to the guitar: thumb on the low E for the two, fingers on the high strings for the three.

Displacement. Loop the phrase starting on beat 1 until it feels natural. Then, without changing the metronome, wait an extra eighth note and start it on the "&". It will feel as if the phrase is falling over at first. Keep tapping your foot on the beat, and it settles into a new groove.

Do these in order. Each one is small. Tick the ones you have practised.

• 1.Three against two

  4 min · 50 → 70 BPM

  1. Count six evenly: "1 2 3 4 5 6".
  2. Left hand taps on 1, 3 and 5 (three). Right hand taps on 1 and 4 (two).
  3. Say "pass the gol-den but-ter" to feel the combined rhythm.
  4. On guitar: thumb plays the low E on 1 and 4, fingers pluck the top strings on 1, 3 and 5.

  You have it when

  • You can keep three against two going for 30 seconds, on the table and on the guitar.
  I practised this one

• 2.The 3-3-2 strum

  4 min · 70 → 100 BPM

  1. Count eighth notes: "1 & 2 & 3 & 4 &".
  2. Accent the 1st, 4th and 7th eighths: 1, the "&" of 2, and 4.
  3. Strum all eighths quietly with the accents loud, then strum only the accents.
  4. Play it over Am and then over a two-chord loop.

  You have it when

  • The accents land in the right places for one minute without drifting.
  I practised this one

• 3.Move the phrase

  5 min · 60 → 80 BPM

  1. Play the four-note phrase from the tab starting on beat 1. Loop it.
  2. Now start it on the "&" of 1, one eighth note later. The notes are the same, but the accents move.
  3. Then start it on beat 2.
  4. Take a short lick of your own and displace it the same way.

  You have it when

  • You can play the phrase from three different starting points while keeping the pulse.
  I practised this one

Polyrhythms collapse when rushed. Start at 60 BPM, count aloud, and speed up only when the two layers stay independent.

• Letting one layer swallow the other. Practise each layer alone, then together very slowly. Say the combined rhythm aloud.
• Shifting the beat instead of the phrase. When you displace a phrase, the metronome and your foot stay where they were. Only the phrase moves.

The 3-3-2 grouping is the rhythmic engine of a lot of Latin, rock and pop music, and three-against-two is at the heart of many African and Afro-Cuban rhythms. Displacement is a soloist's best trick for making a short idea last: repeat it, but start it somewhere new.

Short version (10 minutes)

Three against two on the table, then the 3-3-2 strum for two minutes.

Standard version (about 30 minutes)

Do all three exercises, then improvise for two minutes over Am, displacing one phrase in every four bars.

• Polyrhythm: two divisions of time at once, such as 3 against 2.
• 3-3-2: accents on 1, the "&" of 2, and 4.
• Displacement: the same phrase, starting somewhere else.
• The pulse never moves; the pattern does.

You are ready to move on when you can honestly say:

• I can play three against two on the guitar.
• I can strum the 3-3-2 grouping over a steady 4/4.
• I can displace a phrase by an eighth note without losing the beat.