Watch this clip: http://www.youtube.com/wa...WoF0kP4UCI

if you notice on here, there are 2 drummers drumming at the same time..what is the purpose of that? Ive never seen that before...Im almost finished with the Fred wesley Jr autobio and he talks about seeing 4 drummers playing at the same time..whats the purpose of that?

The same as having two saxophonists, basically. To have interaction between two musicians who just use the same instrument(s).

Coltrane probably started it as far as I can remember (or was one of the first), altough he aspired for "more elastic time". Some heavy metal bands utilize two drummers too, but it's also done for the reason of having two separate sound sources coming from the different sides of the stage. At small venues, where the sound of the non-amplified drum kit is still very dominating, it just means you are effectively filling up the space in a different way than just having one percussionist producing the rhythmic backdrop from one corner of the stage.

I think some swing bands might have had two or more drummers too even earlier.
[Edited 1/6/08 12:48pm]