[Geoffrey Bullock]

I’ve used Audacity to do sound editing with Vegas MS. You’ll have to render out your audio track to an audio file first, ideally using a format that retains as much of the raw audio as necessary. Certainly you’d want to use settings that at least match the audio quality of your source material.

Anyway, make your edits in Audacity – then export to another new audio file (again – keeping an eye on quality settings). Use that file to replace the audio track in Vegas by either deleting and replacing the original track, or add a new audio track and mute the original.

Of course, you need to be sure your editing doesn’t cut anything out of the timeline, or you’ll have a mess of a time trying to synch things back up. But, if you simply export from Vegas – edit in Audacity – then export again; you should be able to simply drop the track right back into Vegas and have everything still perfectly synched.