I am creating a Westley XML that is attempting to mix the audio of a background MP3 and a Video clip.  The background MP3 is 30 seconds long, and should have a constant audio level the entire 30 seconds.  I have a few photos, and a video that should play during the video.

Example Layout:

=== photo ===     ==== video clip =====    === photo ===
                           [      mix transition      ]
=============== background.MP3================

So here is the question, is there a way to maintain a constant audio level on the background MP3 when I'm mixing it with the video clip?  I created a "mix" transition for when the video should mix with the MP3, and I had to set both the start and end properties to "0.5", to get it to mix... so you could hear both clips.  However, the problem is that by setting the background level to "0.5", it drops the level... and thus the background music gets softer.  If I set both of the properties to "1.0", only the top most clip plays.  Am I just missing something obvious?

If I need to clarify, please let me know.