A polyrhythm is a combination of two or more different rhythms that follow the same basic pulse. For example, let’s say you have a 4/4 measure. One rhythmic layer uses the 4-beats reference for that measure, and the second divides the same 4/4 measure into 3 beats. This is referred to as a 3 against 4 or 3:4 polyrhythm. When both rhythms play together, they form an overall rhythmic phrase that is perceived as one.