Controlling sound from an externally loaded swf

here’s my problem.
i have a file called main.swf that has background music.
(below is how the music is loaded)

mySound = new Sound();
mySound.start(0, 100);

and an external.swf that loads into main.swf

external.swf gets loaded on a button click and at the same time it’s loaded the background sound of main.swf is stopped.

all of this works fine.

but when i try to start the sound again with a button in external.swf the sound doesn’t start playing.
(below is how i call on the sound to start playing again)

_root.mySound.start(0, 100);

this seems so excruciatingly simple but i haven’t been able to get it to work for 2 full days.

i’ve tried mySound = new Sound(this); and that doesn’t seem to help.