A decent way I don't know, but there is a way:

thank you, guys. in fact I tried today with FabFilter pro-c and it works quite well, it seems. there's a side chain option with a "in" and an "ext" cases to choose.

Glad to hear it. Will have to try that plugin.

I re-tested the db audioware side-chain comp V2 . I put the side-chain 'db audioware' comp plug-in on both tracks and set the control track (narration) to 'Send' on the plug-in, and set the other track (music) to 'Receive'. To create a prefade scenario, I duplicated the narration track and moved it ahead by 30 frames or so and increased the release parameter. I did not assign the duplicate control track to the master. It also has high and low pass 'send' filters that can be used in or out or the side-chain mode.

Thanks for the interesting explanation.

Unfortunately in the db audioware side-chain comp, user presets cannot be saved (error message) and the default settings return when a project is reopened. This may be a limitation of the demo version. Fortunately, there are not a lot of settings to recreate, and files render OK.

This press release from Magix hints at software integration that would make native sidechaining seem like child's play. Stay tuned.

https://www.magix.com/us/press/detail/news/magix-new-strategy/

;)

Big things are on the horizon. Things that me, and many other people are around these forums, have been begging for since Magix acquired VEGAS. They have finally listened, and a synergy that will benefit all of their products is to come, as this press release hints at.

For those of us who are video and audio editors, Vegas Pro is a beauty and this is a part of its success; but urgently needs a review and updating of its audio system. Let's hope it doesn't disappoint with these changes to come.

I used to do all my audio editing outside of Vegas but have come to appreciate the advantage of editing multi-track audio while being able to see the all the musicians playing it from various angles. Makes a big difference in the synergy of the audio with the video cuts. I'm hoping Vegas keeps advancing it's internal audio resolution so I can do more with its mixes.

As far as I know the main external developers I know have already developed this feature to work in VEGAS.
Vegasaur by @altarvic https://vegasaur.com/voice-over

HOS by @wwaag https://tools4vegas.com/eventducker-2/

Excalibur by @jetdv http://www.jetdv.com/excalibur/audio.php#top

Fasst Apps by @JohnnyRoy http://vasstsoftware.com/product/voiceassistant/

UltimateS Pro by @JohnnyRoy http://vasstsoftware.com/product/ultimate-s-pro/

Of those mentioned above, the most current ones are Vegasaur and HOS that use ffmpeg to automatically analyze the silence in audio events even when there are no empty gaps between the audio events.

Only the official developers have never been interested in creating this feature and I honestly don't have hopes that one day they will create this option natively in VEGAS.

Side-chaining has been wildly used since the early days of analog outboard gear, why Vegas never supported this is beyond me .. but likely the devs are not audio folks.
I recall the days of Sound Forge 3, where the dynamics parameters had non-traditional audio names.