How to Connect a M By Seamus Islwyn ; Updated September 15, 2017.If your computer has a MIDI port on the sound card, or if your MIDI keyboard has a USB port, you can plug the MIDI keyboard straight into your computer.Plug one end of the USB or FireWire cable, depending on the brand, into the audio interface s USB or FireWire port; plug the other end into a free port on the computer.A MIDI keyboard uses the Musical Instrument Digital Interface protocol to send signals to a synthesizer or other sound-generating device.A MIDI port is circular and has five holes arranged in a semicircle.Some audio interfaces draw power from the computer s USB port, and therefore require no other external power source.The MIDI keyboard is connected to the computer through the audio interface.Hook a MIDI keyboard up to your computer, then use it to control your digital audio workstation or any MIDI-capable virtual instrument.Plug in and turn on the MIDI keyboard and the audio interface, if necessary.Plug one end of the MIDI cable into the keyboard s MIDI Out port; plug the other end into the audio interface s MIDI In port.If not, you ll need to connect the keyboard using an audio interface.