Playing background sounds and powerpoint concurrently

My experiment loads a powerpoint presentation, which contains slides with sound files that play immediately when certain slides are displayed. When I told medialab to play a sound file in the background upon loading this powerpoint presentation, the sound file won't play.

The sound files are in WAV format and worked fine when I told them to play during questionnaires.

Any idea as to why this happens and how I can have a sound file in medialab and sounds in a powerpoint presentation play concurrently?

Not sure why a backsound would not load for a PP item. As a workaround, perhaps try loading the sound as a backsound for an [I]instruction item[/I] immediately prior to the PowerPoint item. Put a duration on the instruction item (d1) or even (d0) and MediaLab will automatically continue to the PowerPoint show while the backsound continues.