If your XP-30 is anything like my XP-60, you have to set it up in "Performance" mode. You are allowed 16 "patches" (called "parts" that make up a "Performance" -- trust me it took me days to figure out this bizzare Roland stuff. But we non-Roland pros need each other to sort it out.
The previous post about changing the MIDI on the MPC to get the different MIDI sounds out of your keyboard is correct, but you have to map your XP-30's 16 MIDI channels first in order to get it to talk correctly to the MPC. You cannot play a patch into the MPC and then change the MIDI channel on the MPC and change the patch on the XP-30 and think you are changing anything. The MPC is not reading XP-30 MIDI channels, it is just reading whatever current patch you have set.
This drove me mad, but I sat down with the manual and did the math: 16 MIDI channel Performance Parts on the XP-30 and 16 (1A) MIDI channels on the MPC, hmm, they must be related. I was right.
So, what I do on my XP-60, is have a Performance called "Default" (how original, right?) and on MIDI channel 1 (Part 1) I have a bass guitar patch, on MIDI channel 2 (Part 2) I have a Piano, etc. MIDI Channel 10 (Part 10) is always a drum kit on Roland products for legacy reasons. I save this Performance and it loads everytime I fire up my XP-60.
For each patch (part) you set to each MIDI Channel in the Performance section, hit the MIDI menu button (labeled in the screen) and make sure you have it set to LOCAL OFF, and TX ON and RX on, and make sure the channel you are on, is the channel you have it set to. They make it so you can have it all screwed up, keep it straight. What I mean to say is that Performance Part 3 could be MIDI Channel 16 -- maddening! So match all those up correctly.
I've also found that you have to select the MIDI section on the MPC, hit OPEN WINDOW and set "Soft Thru" to OFF, or you'll get MIDI note loops. Bad, bad, bad.
When you get this all setup correctly, cables connected, etc. when you set your MPC to record on MIDI:1A-Device01 (also know that you can name "Device01" to "XP-30" very cool!) set your XP-30 to the corresponding "Performance" -- in this case, MIDI Channel 1, or the first performance patch.
It is incredibly hard to describe technical information, it would take me 15 seconds to show you. So I took some pics. I happen to have the MPC selected to the 2nd MIDI channel while the XP-60 is on the 1st MIDI channel, but you get the idea:
I might make some mini-movies and Flash-based tutorials on this stuff if I get motivated... and people make enough noise. Why should we all suffer when only a few of us can and share that knowledge?
Oh, and I'm not making this up, listen to a demo of a few patches playing at the same time, with some drums+guitar:
30 second demo
Shawn