Midi problem..

I tried searching the forum, google, my manuals, everything, but i'm afraid I know too little about the subject to even know what to search for...
Let me try to explain my problem. I finally got my asr-10 hooked up to my mpc2000xl after following god knows how many step by step guides, they're hooked up in the midi handshake and all that. I can record what i'm playing on the asr into the mpc, where I lay the drums and do all the sequencing. The problem I'm dealing with now is that when i change instruments on the asr, so does the instruments I already recorded into the mpc, of course, because thats what midi does. But how do I avoid that? Let's say I do a track, I lay the drums on the mpc, play som keys over it with the asr, now i wanna lay down some strings or something but if i change the instrument on the asr from keys to strings so does the part with keys i recorded into the mpc. I hope you understand what i mean because i really don't know what to do. I could imagine i somehow need to assign each instrument on the asr to a different channel, but i can't figure out how to do that.

Please help me!

waiitn for lamp

Thank you for your reply. That is also what i thought i needed to do, i just can't figure out how to do it.
I have tried following the asr-10 manual, and according to that, the asr just need to be set on INST CHAN and all should be good. However this doesn't solve my problem, so what is it i need to do?

I am using a different track on the mpc, but how do i change tracks on the asr? I'm thinking they might not be synced right because i am not even using tracks or recording on the asr. Should i be?

Thanks to your help, i managed to solve my problem. However this caused another problem to arise. I'm not sure whether i should post my new problem on this forum since it is not mpc-related, but i will do so anyway and you guys can just answer if you feel like it.
When changing the midi channel of any instrument on my asr-10, the screen immediately jumps from the Edit->Instrument screen back to just the Edit screen, and the changes i have made is usually reset to whatever they were before. If i attempt to try again, the same thing will happen and the screen will start to glitch and wink or whatever you want to call it. All midi activity will be cut of and i will no longer be able to hear the sounds i have recorded into my mpc. The asr-10 will be in a near frozen state, constantly jumping back to the edit screen no matter what buttons i press. If i keep playing the recorded sequence on my mpc, the asr will soon come up with this message: Error 144 Reboot?
Through google i have learned that error 144 usually means "midi buffer overflow" but i can't seem to find a solution to the problem. If you have any idea of what i need to do or where i can find someone who knows, please help me.
Thank you.