... usb midi interface Superior quality FCC,CE,RoHS Short delivery time 4-in 4-out usb midi interface Model:W-819 Product Description4 input 4 output USB MIDI Interface ... , support Windows XP, vista and Mac OSX. Through controlling the button, this new product can change between USB mode ... port and 4 out port; 3. Can be used to be one port input(can change between input 1, input ...