I am very partial to this mixer. I usually use 2 of these at a gig. Also get to use a Numark AVM-02, while it has some neat effects, it really isn't as good as a V-4, being that is a Audio and Visual mixer, its not good at either.

Edirol Roland V4 MIDI Setup Tips

Took me a bit to figure this out, so I'll share. Read the Manual first, it will help. I built one of these, but it didn't work till I skipped the inverter part of it. So pin 12 of the joystick port(DB-15) goes to a 220ohm resistor to pin 5.

MIDI Setup:
-From Menu --> MIDI Setup -->
-Set MIDI TX & RX Channel to 1
-Those should be default, you may want to restore the "Factory Presets" With TX & RX set to 1 the MIDI Commands should be this.

Example: "B0 0B pp" is the factory default for Video Fader, pp = 0-127 in hex(Velocity Byte)
The first byte "B0" is the MIDI Channel Byte, B0 = Channel 1 (what MIDI RX is set to)
The second byte is the control change, it references what CC# control is changed. So if the Video Fader is defaulted to "CC 11" in the MIDI setup menu. "0B" which should be just "B" but my MIDI Program didn't recognize just "B" it needed "0B" to make 11.
And the 3rd byte is the velocity 00h - 7Fh(0-127), that directs the mixer what level the control should be set to. example: the Video Fader, 0 would be Channel A, 127 would be Channel B, and any number in between the 2 would be a mix of A & B.
Pg. 89 of the Manual has a list of the available CC bytes.