The concept of polyrhythms is an often misunderstood topic. This article will attempt to clarify and explain what polyrhythms are and how they are interpreted and played. We assume a basic understanding of musical notation and rhythmic concepts. None of the material is difficult to understand, although if some of the concepts are new it may take a little while for things to gel. Don't worry if everything doesn't make sense on the first reading. Try to absorb the basic concepts and as you become more familiar with polyrhythms things will start to come together. Polyrhythms are found in just about all types of music. You may discover that you are already using polyrhythms in your playing. Hopefully this article will help you further develop your understanding and allow you to learn and apply new polyrhythms easily.
First we'll begin with a discussion of what a polyrhythm is. A simple definition of a polyrhythm is two or more rhythms played simultaneously. While this definition is basically correct, usually when we speak of polyrhythms we are talking about a more specific relationship between two rhythms. Normally a polyrhythm gives the impression of one musical pulse being superimposed or played against another. In other words we have two different rhythms being played against one another which give the impression of a "cross-rhythm" or "cross-pulse". Perhaps the easiest way to conceptualize polyrhythms is to think of them as rhythmic ratios. For example a ratio of 3 notes to 2 notes, or 3:2, would be considered a polyrhythm. To play such a ratio we must superimpose three notes of equal value over a pulse of two notes. If the ratio were two notes to three notes (i.e. 2:3) we would need to superimpose 2 notes of equal value over a pulse of three notes. Generally two rhythms are only considered a polyrhythm if they have no common divisor (other than one). In the examples above 2 and 3 have no common divisor. There is no whole number (other than one) that will divide evenly into both 2 and 3. The rhythmic ratio of 3:4 would also be considered a polyrhythm. Three and four have no common divisor other than one. On the other hand a rhythmic ratio of 4 notes to 2 notes (i.e. 4:2) is NOT a polyrhythm. Two and four are both evenly divisible by two.