Open a music notation application, such as Sibelius, Finale or Noteworthy Composer. Input notes to create your song and export it as a .MID file. The steps necessary for this will vary from program to program -- consult your application's documentation if uncertain. Save the output file to your desktop.
Download GXSCC and run it. Drag the icon of your MIDI file into the GXSCC window to open it for conversion.
Click the "Config" button, marked with a hammer icon. Open the "Instrument Select" combo box and choose "Famicon like Set" from the list. Click "OK."
Click the "Authoring" button, marked with a page and a sine wave. Wait for the program to convert your original MIDI file into a .WAV with 8-bit-style sounds, compatible with any media player.