Midi Sync to Roland RS-5

Check it, I have the MPC 2KXL and I have the Roland RS-5 Synth and I currently have them hooked up via midi. My problem I'm having is when I make a track and I record (piano from the roland) on track 1 and try to record a different sound (guitar for example) from the Roland on track 2, track 1 changes and so on so forth. I have read the manuals but I guess I am not getting it. How do I change the different sounds on the roland from my MPC while maintaining the original sound selected for each individual track?

Don't be shy.....HELP. This is like my S.O.S. Message

put the rs in multi mode or performance mode, what ever its called for your device. you may need to set up a multi timbral program.