Multiple Sound Volume Control

Hello,

I’m having issues with controlling multiple sound volumes in flash. What I need to have happen is a Background music softly playing while a voice over is also playing.

This is what i have in the first frame of my main timeline

firstSound = new Sound(BGMusic_mc);
firstSound.attachSound("LatinRockMusic");
firstSound.setVolume(10);
voice1Sound = new Sound(Voice_mc);
voice1Sound.attachSound("Voice01");
voice1Sound.setVolume(100);

Then when I want each sound to start I have

firstSound.start()

in the specific frame

and then

voice1Sound.start()

but when it starts to play the voice sound the volume jumps up to 100. I need the first sound to stay at 10 and the voice sound to be at 100.

How would I go about doing this??? Thanks for any feedback.