Often used in the phrase "in the pocket" to describe someone playing a musical instrument in such a way that the groove is very solid and with a great feel. When a drummer keeps a good metronomic pulse (keeping time), and makes the groove feel really good, and maintains this feel for an extended period of time, never wavering, this is often referred to as a deep pocket.

For more information, including the history of this term and its use, read Bart Elliott's article entitled In The Pocket.

Poly means many ... polyrhythm means many rhythms. For there to be a polyrhythm there must be two or more opposing rhythms played, heard or implied at the same time. An early classical example of polyrhythm would be Don Giovanni in which Mozart used 3 different dance-rhythms simultaneously.

The simpliest example of polyrhythm would be 3:2 (three against two) or 2:3 (two against three). However, there are more intense polyrhythms such as 5:2 or 7:4 which go beyond the popular triplet based polyrhythm, using other Odd Note Groupings such as quintuplets (5) and septuplets (7).

Polyrhythms (aka rhythmic contrasts) are the basic rhythmic principles underlying African-derived musics, including Jazz.

Another type of Buzz or Multiple Bounce Roll. The performance typically requires the performer to dig in a bit more, lightly pressing the drumsticks into the drumhead, causing a slight choked sound ... hence the name Press Roll.

See also Multiple Bounce Roll.