ClassABC:ABC Notation

abc, developed by Chris Walshaw, is a language designed to notate music—tunes and lyrics—in ASCII format. It was originally designed for folk and traditional tunes of Western European origin (commonly English, Irish and Scottish) which can be written on one stave in standard staff notation.

Although it has since been extended in the draft standard to support the notation of complete, classical music scores with multiple voices and clefs, abc remains, at its heart, entirely human readable and playable.

From http://en.wikipedia.org/wiki/Abc_notation (go there for a more complete text) Main Page