[Mark Sir Link]

you need to trigger clients to make the song play for them also.

in a weapon everyone has like -MusicSystem try something like

PHP Code:

function onActionServerside(cmd, p1){
  if(cmd == "playall"){
    for(temp.p: allplayers){
      p.triggerclient(this.name, "play", p1);
    }
  }
}

//#CLIENTSIDE
function onPlayerChats(){
  if(player.chat.starts(":start")){
    triggerserver("gui", this.name, "playall", player.chat.substring(7));
  }
}

function onActionClientside(cmd, p1){
  if(cmd == "play"){
    play(p1);
  }
} 


Not tested