I played 'cello for many years and later, traditional Irish music on guitar with my brother on fiddle. I played in the Dowling Orchestra for awhile in the 90's after a friend had told me they needed Cellists. I was only starting to get my chops back when I dropped out (I don't remember why now - the girls, maybe?). I wanted to get back into the 'cello, and remembered the ABC notation system I had run across awhile ago. I thought I might be able to find some kind of editor that could transpose the (mainly) treble clef music that most traditional Irish, Scottish and otherwise Celtic-flavored music is usually written in, into bass clef (since I would prefer to read bass clef than struggle with the treble). I have found I can do this using an ABC music notation program.

ABC is a text-based musical notation system developed by Chris Walshaw which allows one to type (in a text editor like Window's notepad, or directly into an 'ABC editor) the letters of the notes of the song in question. The user can define the value of the note (1/4 note, 1/8 note, etc.), as well as add lyrics, and, in some editors - multiple voices. An ABC editor can then display these typed notes as actual music for print out, and play the song through the computer's MIDI interface.

Since I use a MAC, I had a choice of using one of the many unix ABC notation programs, or one with a MAC graphical interface. I went for the latter and found BarFly to be one of the best.

In the search, I ran across a wonderful site by Laura Conrad, which, incidentally runs on bloxsom! Laura sings medieval music and has transcribed a multitude of songs into ABC notation, and provides them on her site.

However, BarFly has trouble with her stuff (although it can read other ABC notations fine), in fact the lillypond software has troubles with her files too - I've given up on reading them for now. There are so many tunes available, I has the potential to keep me busy for years.

So far, I've only worked on one piece, but luckily my 'cello was still in good shape, and the sound post hasn't fallen again as described in a previous story here.

update Feb, 2012: (from a recent email I sent) abc notation has become one of the primary ways folks share fiddle tunes online. ABC is an ASCII spec which defines how to "code" music using plain text. The benefit of this is that you can share a file (these usually have a .abc extension) which can have one or many tunes in it (all in plain text) which you can then load into an "abc reader" for display in music notation, for print out, hear it played as rendered in MIDI format, or even transpose it (in some readers). Another very cool thing about abc is that there are literally thousands of tunes already on the internet in the format for free (as well as full up multi-voiced classical arrangements) and you can share them easily in plain text in all sorts of ways with your buddies. They're also "readable" in a way, since they're plain text - not in some proprietary mysterious binary format - its just plain text you can copy and paste.

Here's an example of a tune I have been playing lately:

X:3
T:Foxhunter's jig
C:Trad.
S: The Black Book
M:9/8
K:D
||FGF F2 D G2 E | FGF F2 D E2 D | FGF F2 D G2 B | AFD DEF E2D :|
|| B3 BAG FGA | B2 E E2 F G2 B | ABc dcB ABc |d2D DEF E2 D:|
|| fgf f2 d g2 e | fgf f2 d e2 d | fgf f2 d g2 b | afd def e2 d :|
|| gfe dcB AGA | B2 E E2 F G2 B | ABc dcB ABc | d2 D DEF E2 D :|

There is a nice writeup about ABC on the Wikipedia page: http://en.wikipedia.org/wiki/ABC_notation

and you'll find tons of abc formatted music on the Session site: http://www.thesession.org/tunes/index.php (just click the abc tab for any tune)

Theres a cool tutorial if you're interested: http://trillian.mit.edu/~jc/doc/doc/ABCtutorial.html