using MORE then 2 keyboards/modules on 2000xl

Since theres only 2 midi channels in the back of the MPC how would I use 4 different keyboards on the same song?

There are 2 midi CONNECTORS, each of these CONNECTORS gives access to 16 midi CHANNELS.

If you need more info on MIDI then you can always have a look on this site :
http://www.tweakheadz.com/how_to_get_st ... _midi.html

Maybe midi thru on the keyboards? but then u can only use 8 channels on one of your synths... u plug a midi cable out from the midi thru on one of the synths and then put it in to the midi in one the third one. But your synth must be a multitimbral synth. Hope it helps!

that didnt help me much

That article I pointed to explains very detailed how to use multiple modules/synths one the same midi connector.