Yamaha called me today at work.. Too bad I was out to lunch at the time, but the guy was generous enough to leave a message with the answer to my question.... Ok folks here it is.. You CAN hook up a drum machine to the PSR's, and there are two ways to do it.. You can either have the keyboard set as the "master" or the drum machine as the "master". The tech said if you want the keyboard to trigger the drum machine that you really don't have to do anything to the keyboard.. Just set the drum machine's midi sync to external (ext). This way you can control the drum machine from the keyboard. If you want the drum machine to control the keyboard you set the midi on the drum machine to Internal (int), and go under the the midi settings on the PSR and set the "Clock" to External (ext). This way you can control the start and stop of the keyboard from the drum machine.. This way works nice if your drum machine has a jack for a footswitch. He didn't say anything about whether or not you can bypass the internal styles on the keyboard to just hear the drums... I'm not going to bother asking him this because I've already figured it out.. When you sync to the drum machine the keyboards styles will play in sync with the drum machine.. This isn't bad though because there are a few ways around this.. You can turn the accomp volume all the way down and you'll only hear the drum machine. This way works well if you like to split the keyboard, and play manual bass on your left and piano on your right.... If you want to record styles and songs and use the drum machine you can still do this.. All you do is program your patterns on the drum machine... then record the styles without the drums.. The drum machine should play along with you while you record. This works for both songs and styles....