MIDI keyboards are electronic devices that imitate the action of a piano. The sound produced from an MIDI keyboard is the result of a computer's imitation of what a real instrument sounds like. (In the case of synthesizers, it creates a sound that is purely electronic in origin.) Connecting the keyboard can be done on all MIDI keyboard models by using an audio interface, a device that acts like a hub for audio equipment and funnels the inputs to external devices such as headphones, speakers, and computers. Audio interfaces can be purchased at any audio-equipment store.
Plug in the audio interface's power adapter and turn it on.
Connect a MIDI cable from the keyboard's "MIDI OUT" port to the audio interface's "MIDI IN" port. The ports should be labeled in small print above the port.
Plug the headphones into the audio interface's headphone jack (in the front of the audio interface). If the headphones have a skinny jack (1/8-inch), connect the headphone jack into a 1/8- to 1/4-inch converter and plug the converter into the audio interface's headphone jack.
Connect speakers to the audio interface by running a cable from the audio interface's output port (back of the device) to the speaker's audio input port. Remember to run one cable for the left speaker and one for the right speaker.
Play the keyboard to hear the notes in the headphones or speakers.