A MIDI controller is any device that you can use to play (or "control") music notes on a second MIDI device. For instance, if you connect a MIDI keyboard to a sound module, the keyboard works as a controller, while the sound module produces the music. Many devices can function as MIDI controllers, including digital music keyboards, drum machines and even computer keyboards. In order to use your PC keyboard in this manner, though, you will need to configure your PC accordingly.
Download a digital recording program that supports keyboard MIDI control. For Mac users, consider GarageBand (which comes standard with OS X 10.5 and later) or Logic. For Windows users, consider FL Studio or LMMS. If you already use a different recording program that does not support local MIDI control, download a MIDI control plug-in like Bome's Mouse Keyboard, MidiKeys or MIDI-OX. Install the plug-in.
Open your recording software and choose an instrument. In order to use your keyboard as a MIDI controller, you first need to assign it a voice (sound). For instance, you can choose a piano sound, drum sound, bass sound, guitar sound or other instrument sound. In GarageBand, for instance, you would click the "Track Info" pane and select an instrument from the list. In Logic, open your "Mixer" and select a synthesizer under the "I/O" menu. In FL Studio, click "Packs" on the left side of your screen and select a voice. Find the voices within your software of choice.
Access your MIDI control plug-in. GarageBand users would select "Window" from the menu bar and then "Musical Typing," while Logic users would click "Caps Lock" to bring up a virtual keyboard. LMMS users double-click any preset on the song editor view to bring up the keyboard, while FL Studio users must select "FL Keys," accessed from the "Channels" menu. If using an external plug-in like those listed in Step 1, it should appear on your plug-ins menu, unless it operates externally (in which case, open the program). It designates your keyboard as a MIDI controller, even as you operate your recording software.
Begin playing the keys that correspond to the notes on your screen. The animated keyboard will guide you as to which keys on your computer keyboard correspond to which notes on a live instrument. For example, the "A" key on your keyboard commonly corresponds to C2 on a piano. As you play the keys on your computer keyboard, the music will play on the PC based on the instrument you previously selected.