Connect the power adapter to the Motif 6 and to a power source. Do the same with the MPC 2000XL.
Turn on the Motif 6 and turn the volume all the way down, and then turn on the MPC 2000XL and turn down its volume.
Connect a MIDI cable into the MIDI OUT port (the middle MIDI port) or the MIDI IN port (the third MIDI port) on the back of the Motif 6. To play the MPC 2000XL samples with the Motif 6, use the MIDI OUT port; to do the opposite, use the MIDI IN port.
Connect the MIDI cable from the Motif 6 to one of the MIDI IN ports (there are two, so use the free one) or one of the MIDI OUT ports (two of these, as well) on the back of the MPC 2000XL.
Again, the connection you use depends on which device you're using as the controller. If the Motif 6 is the controller, the cable goes from the MIDI OUT on the keyboard to the MIDI IN on the MPC 2000XL. The cable connects the opposite way if the MPC 2000XL is the controller.
Turn up the volume on the Motif 6 and the MPC 2000XL and tap a key until you can hear the sound coming from the slave device. Once you're satisfied with the volume, you're ready to play.