Polyrhythm:

Polyrhythm occurs when two or more different subdivisions of the beat are played simultaneously, but both subdivisions fit within the same overall time signature or pulse. The instruments are playing different rhythms that are based on different subdivisions (e.g., one instrument might be playing in triplets while the other plays in straight eighth notes). However, both are anchored to the same underlying pulse or tempo.

Example:

•One instrument is playing in 4/4 time with eighth notes (2 subdivisions per beat).

•Another instrument is playing in 4/4 time with triplets (3 subdivisions per beat).

Both instruments are in the same time signature, but they subdivide the beat differently. This creates a rhythmic texture where the two different subdivisions interact with each other.

Polymeter:

Polymeter refers to a situation where two or more instruments play in different time signatures that share the same pulse. The time signatures will typically “line up” after a certain number of measures. For instance, one instrument might be playing in 3/4 time while another plays in 4/4 time, but both are aligned to the same basic tempo or pulse.

Example:

•One instrument plays a measure of 3/4 time (3 beats per measure), while another plays a measure of 4/4 time (4 beats per measure). After 3 measures of the 4/4 instrument and 4 measures of the 3/4 instrument, both will align on the downbeat again, having completed their respective cycles.