I've done exactly that. I can see that my keyboard is sending note on/note off signal on the midi out that goes to mpc's midi in but I can't hear anything (I'm attaching a screenshot,also). Maybe the settings aren't just right?
MIDI TAB:
Multi Timbre: OFF
Active track receive channel: ALL
Soft thru: OFF
Sequence change by program change: OFF
MIDI out after touch: NO
SYNC TAB: (don't know if that's really necessary)
Sync in: 1 (Slave)
Mode: MIDI CLOCK
Receive MMC: OFF
MAIN TAB: (don't know if I'm correct here)
i.e. Set to truck 2 DRUM
Pgm: The program I use
A01: A02: etc some samples I have on
MIDI: OFF
Correct me if I'm wrong.
Forgot to mention that I use JJOS2XL.
When I press a key on the midi keyboard channel 1,on both usb/midi (which goes to akai mpc's midi in) and keyboard midi, goes green.