Found this software for composing your own music
http://musescore.org. It lets you edit music using sheet music notation. Files can be exported as .mid, .mxl, .wav, .ogg, .mp3, as well as several other formats. It also accepts SoundFont .sf2 files, so you can download 8 bit sound files and instantly change your song into a retro chiptune song.
There is also a site
http://musescore.com, where people share music they created with MuseScore.
