POLYRHYTHMS are the simultaneous occurrence of two or more sharply contrasting rhythms. They equally divide the measure—or beat(s)—into opposing sets of equal pulses that have a greatest common divisor of 1. In other words, these sets of pulses contain rhythms that are typically unable to divide into each other.
Both rhythms can be multiplied together, however, to obtain the lowest common multiple. This, in turn, will provide the counting for a single composite rhythm.
The most common example of a polyrhythm is the 3:2: