Polyrhythm

Polyrhythm is the original motivator of libmetro. Polyrhythm as defined by britannica.com is:

>Polyrhythm, also called Cross-rhythm, the simultaneous combination of contrasting rhythms in a musical composition. Rhythmic conflicts, or cross-rhythms, may occur within a single metre (e.g., two eighth notes against triplet eighths) or may be reinforced by simultaneous combinations of conflicting metres.

I first learned of polyrhythm through metal bands (Meshuggah, Animals as Leaders, Periphery, etc.):

Polyrhythm features in African music (and may have even originated there):

libmetro representation

Polyrhythms are expressed rather simply in libmetro. They need to be manually constructed in a single measure using the least common multiple of both rhythms, which is a familiar exercise to anyone studying polyrythms or following basic tutorials (as I did - linked right below).

Resources, tutorials:

• https://bouncemetronome.com/video-resources/polyrhythms
• https://blog.landr.com/use-polyrhythms-get-perfect-beat/
• https://www.youtube.com/watch?v=_37pioTK_gA
• https://www.youtube.com/watch?v=b29H5RLcijs

As before, the metronome files below can be viewed here.

3:2 example

To create a 3:2, we need to find the LCM of 3 and 2, which is 6, spread the triple at indices 0,2,4, and the duple at indices 0,3:

poly_32.txt, file format 1:

measure_length 6

0 sine,440.0,10.0 drum,73.42,100.0 drum,92.5,100.0 drum,207.65,100.0 drum,185.0,100.0
1 sine,440.0,10.0
2 sine,440.0,10.0 drum,73.42,50.0
3 sine,440.0,10.0 drum,207.65,50.0
4 sine,440.0,10.0 drum,73.42,50.0
5 sine,440.0,10.0

This looks better in file format 2, in poly_32_format2.txt:

1 0 1 0 1 0
1 0 0 1 0 0

You'll see see I added sine wave beeps/clicks to make clear how the triples and duples are overlaid on 6 beats:

3:2, 250bpm:

2:3 (inverted timbres of 3:2), 250bpm:

4:3 with a pedagogical twist

There's a fully-fledged pure-C++ 4:3 example. where one can specify how many measures of 4, 3, 4:3, and only clicks (no beats) to play.

The idea is that you could practice X measures of 4, Y measures of 3, Z measures of 4:3, and W measures of only clicks (on which you're expected to correctly play the 4:3), repeated over and over. This can perhaps be of value to drummers.

Note that this concept is expressible with the text file method, but requires one to copy/paste blocks of measures (and change the indices manually), which is tedious.

Test run with parameters 2 2 2 2 300, i.e. 2 measures of 4, 2 measures of 3, 2 measures of 4:3, and 2 "blank" measures of just clicks, at 300bpm:

5:3

poly_53.txt, file format 1:

measure_length 15

# 5:3
0 drum,73.42,100.0 drum,92.5,100.0 drum,207.65,100.0 drum,185.0,100.0
3 drum,73.42,50.0
5 drum,207.65,50.0
6 drum,73.42,50.0
9 drum,73.42,50.0
10 drum,207.65,50.0
12 drum,73.42,50.0

poly_53_format2.txt:

1 0 0 1 0 0 1 0 0 1 0 0 1 0 0
1 0 0 0 0 1 0 0 0 0 1 0 0 0 0

5:3, 300bpm:

More complex example

A suggestion from Victor of a more complicated polyrhythm - named '35_swing' because it can be thought of as '3/5, 5 as a swing pattern':

poly_35_swing_format2.txt:

1 0 0 0 0 1 0 0 0 0 1 0 0 0 0 1 0 0 0 0 1 0 0 0 0 1 0 0 0 0
1 0 0 1 0 1 1 0 0 1 0 1 1 0 0 1 0 1 1 0 0 1 0 1 1 0 0 1 0 1

At 394bpm: