abcpp is a simple yet powerful preprocessor designed for, but not limited to, ABC music files.
The only serious problem with ABC is that it was originally designed for melody, not for harmony. In simple words, this means that you can only write music for a single instrument or voice. This is an example of what ABC can do; it sounds like this. Although it works beautifully for simple tunes and folk music, it can be not enough for Western classical music.
Some ABC applications implement unofficial extensions to the ABC language that make it possible to write polyphonic music. The purpose of the ABC Plus project is to provide software and documentation for this extended ABC. Here is an example of classical music written in ABC Plus; it sounds like this.
All RPMs available from this site were built on a Mandriva 2006 GNU/Linux machine.