I've read that one drummer will praise another by saying they can play "in the pocket" or something like that. I'm not quite sure what "pocket" is. I don't think it's the same as just playing in time - you expect drummers to be able to do that. So would some knowledgable drummer explain what "pocket" is, and also - do non-drummers, i.e. brass players need "pocket", and if they do, how do they get it?