Johnny Ringo, I'm not sure if this answers your question, but we use Hypercube Transcoder to convert the AC3 files into six mono wavs that we import into Sony Vegas. In a situation where we want to change the music for a scene, we delete the other five channels and only keep the center channel. But, most of the time, there's still a trace of music in that one channel, so if the new music doesn't cover it up, or throws it off in any way, we go in and try to manually remove all sound that is not dialogue. It's not always perfect, but will often pass pretty well. In many cases, we have to completely replace specific sound effects and other ambient noise.

For the trailer, we used this technique alot.

I'll keep this subject in mind for one of the webdocs. Thanks for your interest.

--ID