The one MIDI file I heard for The Butcher Boy had just the melody line. It matches up with what I heard on the Upstairs, Downstairs episode "I Dies For Love", which was made in 1971 or 72 (available on video, I got mine at my local library), so the music obviously must be available from some obscure source. :)

I am presently working on a MIDI file for it with both bass and treble clef, so it is a little more interesting and effective to listen to, for my website Melody Lane at http://www.melodylane.net. It should be up online in the folk music section, in a day or two.