Help
First of all, I didn't write the programs which produce the output.  I wrote the code to join them together and give them a user-friendly (I hope) front end. You can find links at abcnotation.com/software to the programs abc2midi which produces MIDI output, abc2abc which does transposing and other jobs, and abcm2ps which produces postscript output.  Then I use Ghostscript to convert the Postscript to PDF which can be displayed and printed by several programs, and Timidity++ to convert MIDI to WAV followed by Lame to convert this to MP3.  I also use GeneralUser GS SoundFont which makes the instruments sound much more realistic than the standard SoundFont which comes with Windows.  Aren't you glad you didn't have to do all that?!

If yopu want to learn more about ABC, a good place to start is the ABC Standard.

This is what the buttons do:

• Home: Returns to my Home page if you're completely stuck.
• Chords below: Displays music British-style with chord symbols below the stave and the bass note of a chord appearing in lower-case below the chord name.
• Chords above: Displays music American-style with chord symbols above the staff and the bass note after the symbol, e.g. Gm/D.
• Bigger: Displays music in a 50% bigger font, usually 4 bars to a line.
• Smaller: Displays music in the standard size font, usually 8 bars to a line.
• Letter: Prints on American letter-size paper.
• A4: Prints on European A4-size paper.
• Play MIDI: Outputs a MIDI file which can be played on your computer (though probably not on your SmartPhone or Mac).
• Play MP3: Outputs an MP3 file which is much bigger than a MIDI file but can be played on anything.
• Print: Outputs a PDF file which can be printed on your computer.
• ABC source: Outputs the source of the music, with my %% commands prefixed.
• Viola on: Converts the tune from treble clef to alto clef and transposes it down an octave.
• Cello on: Converts the tune from treble clef to bass clef and transposes it down two octaves.
• Speed: has two options:
  • Slow: Plays the tune at half the initial tempo and ignores any changes in tempo.
  • Speed: Lets you specify the exact tempo you want.
• Change key: Enter the number of semitones you want to transpose the tune up or down, then click the Go button.
• Multi-Play: Lets you play the tune a number of times, with an introduction and a final chord — you can even specify the instruments for eact time through the tune.

Many settings are remembered for the duration of your session, so you don't have to keep specifying Chords below or Bigger.