There are good reasons to render wild audio to vision in one file when editing with Vegas.
When it's in the one file Vegas knows it has to keep it in sync and if it gets slipped out of sync it'll raise a red flag. You don't get that any other way unfortunately.

To answer the OP's question, when I've done this I use one of the XDCAM variants . The mpeg-2 codec it uses is easy to edit and the audio is uncompressed. One can also have more than one track of audio which can be very useful at times at times. Resulting file sizes are not "small" I suppose however most higher compression codecs generally also use lossy audio compression.

Bob.

Thanx for the suggestion but it's not really that easy. I need to send the various pieces around for comment via the cloud and our internal server where I work. I'm looking for someone who knows the fastest way to blend the new audio whilst maintaining the video quality and hopefully creating a small, more manageable file.

For example, I just did a 10 minute interview and the Canon 60D file came out to over 3 GB. I've tried a few of the codecs and they produce a much smaller files but I assume someone out there has already dealt with this situation and can guide me to the BEST solution (if there is such as thing!).

Maybe I'll send in an official question to SONY and receive silence like my last inquiry from a few months ago.

"I'm looking for someone who knows the fastest way to blend the new audio whilst maintaining the video quality and hopefully creating a small, more manageable file."

Quality, size, speed. Pick two.

If you're just sending a preview file around, use mp4 as your render format. Internet template should do. A segment is rendered out in Vegas using a loop region.
Again, rendering to a new track seems superfluous.

[I]" I need to send the various pieces around for comment via the cloud and our internal server where I work."[/I]

That's a very different scenario to "render to new track".

[I]" I'm looking for someone who knows the fastest way to blend the new audio whilst maintaining the video quality and hopefully creating a small, more manageable file."[/I]

File size and quality are inversely related so you are forced to trade one off for the other. The way you get what you want in Vegas is to render to a file. If you only want to do that for a portion of your video then create a "looped region" and tell the Render As dialog box to only render that region.

I'd suggest using one of the h.264 codecs that Vegas supports. That's a very efficient coded so good quality and small file is less of a compromise. If you really want to get the file size down then use Handbrake to encode to the X.264 coded. Heaps of threads on how to do this in this forum, use the search facility.

Bob.

musicvid10's suggestion is really practical and the easiest way to go. The only thing that you have to decide is which of Vegas Pro's many render choices is the best fit you. If its only for preview for stakeholders, take musicvid10's recommendation of an mp4 render.

A point to clarify: In Vegas, MP4=h264.

Internet template will give you a compact 720p file that can be sent around your cloud servers and easily played. Handbrake is spiffy, and my tool of choice, but probably takes more time as you will do an intermediate render.

Thanx for all of the responses.

I think I found a good working codec. SONY AVC/MVC....Internet 1920x1080-30p and I add "BEST" under Project Settings. This seems to do a nice job on short 10 second sections of my source I've been experimenting with. I don't notice any video artifacts and the sound is what I wanted in the first place. I'll try it on the whole 10 minute interview later today and see how long it takes and how big the file ends up.

I seem to have gotten the "Match project settings" in the rendering screen to finally offer some suggestions. I had originally tried this method but either nothing showed up or I didn't realize I needed to click on the main headings to see the various codecs that apparently do match my project settings. In any case, I've gone through many of these project matching codecs, tried adjustment like setting them to "BEST video quality, etc. but none seem to give me an "identical" quality of video although some look a little better than others.

Is there any way to simply sync the audio files in Vegas or another program, then delete the original audio file and then save the video with the new "better" external audio file without rendering it so that there is no loss in video quality?

"Is there any way to simply sync the audio files in Vegas or another program, then delete the original audio file and then save the video with the new "better" external audio file without rendering it so that there is no loss in video quality?"

Why can you not simply import your 60D footage onto timeline. Then insert new audio track, import your external recorder audio and sync - either manually or using pluraleyes. Then simply select the 60D footage and ungroup, then delete the 60D audio track, then create new group of 60D video track with (imported and synced) external audio. Am I missing the point???