What you mean by global sound system?
Just it's simple. You Cannot Play Sound Through All scenes/rooms. Of course you can do it if the sound is background music. But let's say this situation.
You're in horror game. And you just activated the event when the suspenseful music starts playing. But the music has no loop only play once.
Now you just did in through editor. For example, you did it by start sound, not start background music. Of course the music starts playing and ends but doesn't CONTINUE on next scene. It immediately ends when you switch scenes.
So I CANNOT make this atmosphere when the protagonist goes mysterious house and wandering around the whole rooms (this is just an example).
Now you did it by start background music. The music continues on next scene if you check 'continue music from previous scene blah blah blah' in scene property. But the problem is IT LOOPS FOREVER no matter you switch scenes or not.
This is why global (control whole scene's music or something like that) sound system is necessary for me and other developers.
If it exists, then I can manually set the loop option of the music and... you know what I'm saying. lol