In a tech tip a couple of weeks ago (12/18/00) we briefly mentioned some reasons why bass and vocals are usually panned to the center of recordings. Since then many readers have reminded us of the one reason we forgot to mention as to why bass and kick drum have historically been panned center. Not that it matters much these days since I doubt many of you are sitting at home with cutting lathes kicking out LP's, but back in the vinyl record days, engineers had to be cognizant of the physical/mechanical properties of records and players. There are limits to what this mechanical system can do. Too much low frequency content, especially when panned to one side, produces grooves that a typical playback stylus can't track, assuming the record could be cut in the first place. Of course, this had almost nothing to do with decisions to put vocals in the center, and contrary to what many readers wrote, aesthetic concerns drove a lot of this, making the need to solve the technical problems less important. The good news is that unless you are producing music for distribution on vinyl records you need not worry about all this minutiae. If you are producing music for vinyl you should talk to the mastering engineer before doing your mixes to be sure you comply with all the currently accepted techniques for playing back music on vinyl.