There is little know feature that allows you to use your own music in TOJ. You may noticed that all resource directories are packed to SJE.JHH, but music directories are exception. I think they intended to allow user use own music.
Put your music into skin\music\default folder, number of files and their names do not matter, but your music must be in ogg vorbis format. If you know any easy to use program that can convert music from common formats (like MP3) to OGG, please let me know in this topic.