So, let me get this straight here. You have all your sounds on the timeline within movieclip holders. Is that correct?

First question is, why? Are you syncing things to that sound?

If, this scenario I'm mentioning is correct then I'd say to put one blank keyframe at the beginning of your movieclip holders. Then put the sound starting on frame 2. That way once they're loaded you can tell them to stop, and when needed, they can go to frame 2. Do you have a source file you can send for example?