A polyrhythm is two or more simultaneous rhythms played at the same time. These rhythms, however, cannot be the same rhythm. Both rhythms will be played under the same time signature, but they will be contrasting rhythms. One of the easiest polyrhythms is 2 over 3 or 3 over 2. This is simply one rhythm that will play two beats in the same space that it takes another rhythm to play three beats.

One way to think of a polyrhythm is to think of each rhythm as a frequency or wave. In the diagram below there are two frequencies or rhythms playing simultaneously. Where the wave line touches the line in the middle a beat is produced. Although mathmatically the center line usually means zero, it was easier for me to demonstrate what I'm talking about this way. The blue wave plays two beats in the same time it takes the red wave to play three beats. Each rhythm or frequency is perfect in itself, however, when played together they are out of synch with each other except for where they play together on one.

For an even more in depth understanding of what a polyrhythm is check out Marc Zoutendijk's polyrhythm definition and examples at http://www.xs4all.nl/~marcz/Polyrhythm.html