can we do something like this with X2 ? would be awesome!
https://www.youtube.com/watch?v=MzXRgcnzivM

Not sure I follow ? What is it on there that you can't do ?

work on the waveform of the clip, cut and raise volume directly in, changing directly the waveform.
 

Oh, ok..... so it's just like clip gain envelopes then, but instead of showing the env position, the waveform itself changes. Don't see it as a big deal personally, but I guess seeing as how applying a clip fade is currently reflected in the waveform in exactly that way, that it should be possible to implement it for clip gain envs if there was a demand for it.....not that I know the first thing about programming !

You can do this in Sonar... Process/Apply Effects/Gain easier if you set this to a binding, (like “Y”)

FWIW I think your trying to use your eyes more then your ears. My experience has been that this is a big mistake

I wonder how they did it with tape? 

Note that this process is destructible, you can't “undo” once project is saved.
 
More Info... http://www.cakewalk.com/D...p=EditingAudio.18.html
 

Bent, really good idea, but when i select a part and change gain there, a big scratch happen in the sound at the start and the end of what i selected.
maybe if i bounce it with radius but i'm not an adepte of it. lose audio quality each time i bounce.

Cut at zero crossings. You can set this under the snap settings.

PsychatoR
Bent, really good idea, but when i select a part and change gain there, a big scratch happen in the sound at the start and the end of what i selected.
maybe if i bounce it with radius but i'm not an adepte of it. lose audio quality each time i bounce.

Radius isn't the answer, choosing the right point to cut is. 
 
I do this all the time with vocals when I want to hit a compressor with a consistent signal in order to use minimal compression. If I'm concerned about the destructive aspect of editing, I work on a copy.
 
You can also use clip Gain Automation and render. Or if you want to take this to the limit, open in an editor like Sound Forge or Wavelab.