Backsound for just one item?

[jarvis24]

Sometimes you will have multiple media clips in your session and they vary in volume. Some play too loud, others not loud enough. Now you can embed an executable item at any point called volume.exe located in the C:\MediaLab\Utilities\Sounds folder. Copy this file into your experiment folder. Anywhere in your experiment add an executable item and in the filename field, type volume.exe. In the parameters field enter (c5) where 5 is a volume setting from 1 to 10. For max volume, enter (c10) and for min volume enter (c1). Any integer value from 1 to 10 is ok. You'll get a brief, "please wait one moment" message while the volume is adjusted after which you can click to continue.

from: www.empirisoft.com/medialab/help/miscellaneous_features.htm