Connect your digital MIDI interface with your computer, if you have one. If you don't have a digital audio-MIDI interface, proceed to Step 2. A MIDI interface can be a drum machine, MIDI-capable musical keyboard, or a simple MIDI-triggering device. Some MIDI consoles connect to the computer with a USB cable. If you are using a device with MIDI inputs but no computer interface, you will need an Audio-MIDI interface that will connect to your computer's USB or Firewire port.
Install your MIDI-capable software. Often, MIDI-capable software is called a MIDI sequencer. There is a multitude of MIDI-capable software available, and if you have played around with audio freeware, it's likely that you have a MIDI-capable software platform already. Professional programs for MIDI sequencing include Reason and Finale. The free audio software program Audacity has a MIDI-sequencing capability.
Configure your software for input and playback. To do this, you will need to make sure that your software recognizes your computer's sound card and your MIDI input device. If you are programming MIDI without an input device, you only need to set up your sound card for playback. Most MIDI-capable software has a setup menu that is called "Preferences", "Setup", or "Options" and can usually be found in the "Edit" or "Setup" toolbar of the software program. Consult your software manual for details on how to set up the MIDI software you have.
Start a new song on your audio software. Usually, PC audio software will begin a new file if you visit the "File" menu and choose "New", or use the quick-Key Ctrl-N.
Open a new MIDI track on your software. You can often start a new track by visiting the "Track" menu and adding a new instrument or track, as in Pro Tools. In Reason, you must add a sequencing track. Some simple MIDI sequencers only allow you to use one MIDI track to program your MIDI song. The advantage to multiple MIDI or Instrument tracks is that a multiple-track environment will allow you to use multiple instruments and create a band or orchestra sound.
Pick a sound. Many MIDI software setups choose a default sound, but with some software, you will not be able to hear the melody you play without choosing a sound first. Some MIDI software will allow you to choose your own sound for MIDI playback, usually in the form of an aif or wav type file, but some MIDI software will only use a limited number of included sounds.
Record your MIDI notes into the track. If you have no MIDI interface like a music keyboard, you will need to place the notes manually using your mouse. If you have a keyboard connected to your computer, you should only have to initiate the record function by enabling the chosen track for recording if necessary, then pressing the "Record" then "Play" button. At this point, if your keyboard if properly connected to the computer, your keystrokes should be recorded as MIDI into the MIDI software.
Export your MIDI song for playback. Your audio software should have a function called "Export" or "Convert" which allows you to change your MIDI song into an mp3 or wav file for playback through a common audio file playback software like ITunes or Foobar.