In this wiki I1) will store all my private sheet music (mainly songs). Due to copyright issues most of its content is restricted and can only be viewed by me and a few friends.
But all traditional music can be viewed and edited by all visitors!
ABC is a musical notation language. See http://abcnotation.org.uk/ for more information.
If you already know how to use ABC: Just type in a complete abc tune (beginning with X:) surrounded by
</abc>. That will output an image of the sheet music, linked to the corresponding midi file.
It is even possible to transpose each abc automatically. Just add the amount of semitones2) as one or more 3) parameters after
<abc 7 -5> will transpose a fifth up and a fourth down and will display the transpositions beneath the original key.