Here goes your answer buddy.
"2nd sequence feature. You can assign a second sequence to be played with the currently selected sequence. This is not as much as it seems at first. All you get is to select one sequence to basically play 'in the background' for any sequence that is selected in the main screen. OK, an example would probably help. This is buried in the MISC screen but I don't know why. I go there and select SEQ-9 as the 2nd sequence. When I go back to the main screen, it indicates there's a 2nd sequence. I Start SEQ-1, and SEQ-9 will run at the same time. I switch to SEQ-3 and SEQ-9 will still be running, I switch to SEQ-2 and SEQ-9 will still be there until go back to the MISC screen and turn this off. I'm not sure why this feature is even there. I guess if you want to try different basslines with one sequence of percussion. I dunno."(mpc200xl)
http://www.mpc2000xl.com/track.htm
Nicole