MPC, MIDI INSTRUMENT PATTERN OVERLAP

First post! Here's the situation. I have and MPC 2500, Axiom 49, Firestudio project, and Cubase LE 4. I have my Axiom running into MPC (MIDI IN1), MPC MIDI OUT A Going into my Firestudio MIDI in. Here is my problem. When I play a vst instrument (guitar for example) and then load a second instrument (flute for example) the second instrument will play the pattern I used for the first instrument. Seems as if i need to do something on my Axion to separate the two instruments and then on the MPC on the main screen, use MIDI 1a for one instrument and 1b for the second and so on.

define midi channels per insturment... if everything is set to respond to channel 1 (the usual default), then everything will respond to channel 1.