mob/var/tmp/current_music // track the mob's currently playing music
turf
    /* defined for all turfs so we don't need to do 
        anything but define soundfile for each one. */
    var/soundfile
    Entered(O)
        // O just entered this turf
        if(ismob(O))  // O is a mob
            var/mob/M = O  // get a mob alias to O
            if(M.current_music != soundfile)
                // mob's current music doesn't match the soundfile
                M << sound(soundfile, repeat = 1) // play the music
                M.current_music = soundfile // track mob's current music

    title_music
        icon = 'blank.dmi'
        icon_state = ""
        soundfile = 'Go go go Naruto.mid'