Download or purchase a digital audio program that contains built-in software synthesizers for recording. Examples include Cubase, Logic, Pro Tools, FL Studio and GarageBand.
Plug your MIDI keyboard into your computer's USB port using a MIDI cable and a MIDI-to-USB converter cable. Plug one end of your MIDI cable into the "MIDI Out" port on your keyboard, and the other end into the "MIDI In" port on your converter. Then plug the USB end of your converter into your computer.
Open your digital audio program. Simply locate it on your computer and click the icon.
Select an instrument track for recording. "Tracks" are simply recording spaces that most often appear as horizontal bars across your screen, typically labeled with names like "Audio Track 1" or "Instrument Track 1." If no instrument tracks show up on your screen, choose the "New Track" or "Create New Track" option from your task bar or navigation bar. Sometimes this option will also appear beneath the "File" menu. Most importantly, make sure to choose an "instrument track," sometimes called a "software track," and not an "audio track."
Access the software synthesizers--sometimes called "patches" or "software instruments"--in your digital audio program, and select a "Piano" setting. For the best sound, choose a "Grand Piano" setting if available.
Verify that your digital audio program receives signals from your MIDI keyboard. With your instrument track selected, try pressing keys on your MIDI keyboard and see if your program responds with sound. If not, click your "Preferences" or "Options" feature and select your MIDI device as an audio input source.
Press "Record." Usually this will appear as a button with a tiny red circle in the center, somewhere in your main window.
Begin recording a beat using your MIDI keyboard. Play just as you would on a normal piano, and the sound will transmit onto your computer with the piano setting that you previously chose. Try different note patterns, chord progressions and sequences until you find ones that work for you. You can always delete unwanted recordings and try again.
Press the "Record" button a second time to stop recording.