Can someone clear what midi bus really is?

Dude, what are you talking about? "Midi" is a computer file and a hardware interface to make music. "Bus" is either a computer term or a multi-passenger vehicle. "4WD" means four wheel drive, and it is extremely rare to see a station wagon or a bus with that. "Station wagon" means a 4 door vehicle with a high roofed luggage space in the back.