A MIDI keyboard uses the Musical Instrument Digital Interface protocol to send signals to a synthesizer or other sound-generating device. Hook a MIDI keyboard up to your computer, then use it to control your digital audio workstation or any MIDI-capable virtual instrument. 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. If not, you'll need to connect the keyboard using an audio interface.
Plug in and turn on the MIDI keyboard and the audio interface, if necessary. Some audio interfaces draw power from the computer's USB port, and therefore require no other external power source.
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. A MIDI port is circular and has five holes arranged in a semicircle.
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. The MIDI keyboard is connected to the computer through the audio interface.