... time 4-in 4-out usb midi interface Model:W-819 Product Description4 input 4 output USB MIDI Interface, support Windows XP, vista and ... mode and Through modes as below: 1. Used as USB MIDI with 64 channels, 4 input ports, 4 output ports, user ... and output port in computer; 2. Can be used as MIDI extender, with the direct connection of 1 input port and ...