[MIDI Connection] First you have to make the connection via the 5-pin MIDI jacks to one or more keyboards so that it can transmit the MIDI note information. You can directly connect up to two keyboards (for UPPER and LOWER registers) to the B4000+. If you also want to connect a bass pedal to (for PEDAL register), you have to merge two MIDI signals at one input with a “MIDI Merger”. These devices are available at your local dealer. [Audio Connection] You can connect the B4000+ to either headphones (low impedance models recommended) via the PHONES output, or to either active speakers or a mixer via the AUDIO jack. Please note that the AUDIO jack is an unbalanced stereo jack. So for most types of connection you will need a Y-split cable, which puts the right and left channels on separate cables.