How to create an envelope from existing audio?

I did search for this really--I found good advice on how to copy envelopes--great stuff.
 
I'm trying to figure out how to have the volume "profile" of an audio track generate an envelope which could be pasted into other tracks, so, when the said audio track got louder (in its own content) the envelope would mirror this volume curve.   I've been thinking how a sidechained compressor would do the opposite of this, but still not generate an envelope for me to use elsewhere (or would it?)
 
This sort of thing could be done in a CV environment; I think there used to be a Moog hardware device (maybe an envelope follower) that would generate control voltage in response to volume.  I'm pretty sure there is some dynamic utility in Reason that does it too. I'm looking for something to automatically draw this for me.  Sure, I guess I could just get out the pencil tool and carefully follow the ups and downs of an audio track, but this must be do-able by the program itself, right?
 
Thanks in advance for your patience with me on this.  It very likely could be something really obvious; I discover these things in SONAR just about daily.
 
LJR
 
 
 

Not exactly what your looking for but Waves vocal rider and bass rider sort of do that in reverse and can write volume automation envelopes. They each have a side chain to use other sources to influence the output. Melda and Hornet have similar plugs.
 
Rocky

I had to open this thread because i have no idea what it means. I will go read it now.........

Also, Blue Cat Audio plugins have this capability. On just about every plugin they have, they have the capability to write automation envelopes or MIDI CC I think, too, based on information from the plugin. It will also allow you to reverse whatever the data is, so, for instance, it's possible to write a ducking envelope for other tracks based on the waveform of another. I've used this function for audio several times via their Digital Peak Meter Pro (which also, BTW, is one of the best meter plugins out there).

Anderton
Dig out your pre-X3 SONAR distribution files and install the AN-879 Analyst, which has a very cool multiband envelope generator function. Also, check out the article I wrote in the February 2015 issue of Sound on Sound that describes the AN-879 as well as other ways to turn audio into automation data.

That's pretty cool - saving the output to a write automation lane.
I'll need to experiment to see what other plug-ins can do that.
 
The way I usually do this is to make a filter+envelope-follower in Reaktor with a converter to change the audio data output level to a MIDI message at a interval.

Thanks all for your help on this.  I don't have my pre X3 files but I imagine I can find them somewhere somehow.  I vaguely remember the Analyst; time for a re-visit.  I don't have the advanced workshop video either, but I'll find it.