As you may have noticed, all the music on this site is released under the Gnu Public License. This means you are free to use it any way you like, and modify it for your own purposes, with a few not very onerous conditions.
I do this because I don’t expect everybody to want to use it exactly the way I do. Specifically, I often find dead-tree printed music is in the wrong key or has the wrong clefs, or too many bar lines or something that makes it harder for me or the people I play with. And then I wish I had a copy in lilypond or ABC or even MIDI so that I could just change it. So when I publish my transcriptions, I put up not only the PDF file my group plays from, but the ABC and/or lilypond source and the MIDI output.
I got an email last week from Christoph Dalitz, who said:
I am pleased to let you know that some of your music editions
published under the GPL have found an unexpected use in a
use in a research study on automatic staff line removal
(a preprocessing step in OMR). The study has meanwhile
been finished and that the results have just been published
in IEEE TPAMI:
C. Dalitz, M. Droettboom, B. Czerwinski, I. Fujinaga:
A Comparative Study of Staff Removal Algorithms.
IEEE Transactions on Pattern Analysis and Machine Intelligence,
vol. 30, no. 5, pp. 753-766, May 2008
You can read the study here
So when you wonder what use free information is, think of the future generation of automated music scanners which will be better because of the people who put free music up on the web. As well as of the people who can play my music in the clef and key they want it in.