Akai MPC 5000 Reference Manual page 49

Connect the MIDI OUT of the keyboard to the MPC5000's MIDI IN, and the MPC5000's MIDI OUT to MIDI IN of the external sound module.
If you select it to the OFF or No., the MPC5000 does not play internal programs. If you select it to the No. and set MIDI Program number,
MPC5000 transmit the MIDI Program number to the external sound module for selecting the sound in it when the sequence is selected.
Here, you set the MIDI channel to send the MIDI data on. Set the same channel as the one on the sound module.
If you don't hear any sound, check the connection and make sure you have the correct settings for the keyboard and the sound module.
The recording starts after 4 counts.
By default, sequence is set to 2 bars. After recording for 2 bars, the MPC5000 will start playing back the recorded performance. If you make
another performance with pads, you can add the performance to the currently recorded one. This is called 'overdub'.
This cancels the currently recorded performance data and starts the new recording.
This plays back the currently recorded performance and you can add the new performance by hitting pads.