CrudeMik - I'm still learning a great deal here, and audio is definitely NOT my specialty. However, I have just a hunch that part of the deal is because it's all set to On start of layout. Something tells me that's part of the conundrum. While it's working for one emitter, even though you have the For each going, the layout has since already started...come and gone. (The green arrow of the event, as I'm sure you clearly know already, signifies it's waiting for a singular, specific instance of that event...the start. Can't have multiple starts, per se. Certainly not of the layout. ... Er, correct me if I'm wrong.)
Since it's working for one emitter, I'm guessing you just need to set it up so it's a different event that isn't looking for a one-time occurrence.
I really don't know, but I hope that helps somehow. Hopefully this will help me learn something, too, once you find the solution.