I'm working on a cover of the song 'Hey Mama' by David Guetta (and a bunch of other people). The song uses a sample of 'Rosie' from field recordings made at Parchman Farm by Alan Lomax in the 1940s. There are two components of the sample, a vocal part and the percussive sound of picks hitting rocks. The percussive sound overlaps the vocal parts in places. On the original track it sounds like David Guetta is able to control the level of the picks transparently. The third time he uses the sample. the picks are barely audible.
What I think I want to do is isolate the percussive sound so I can phase invert it and control its level without causing the vocal part to drop out noticeably. The hard part seems to be isolating the percussive sound, it's slightly different every time. It was trivial to get the sample beat matched with the song in Sonar using Audio Snap, I get a bit of phasing but it's close enough for rock and roll.
Is there a workflow in Sonar that I can use for this?
Maybe there is some way I can pervert the drum replacer to pull it off?
What are the best tools to use?
Thanks!
 

If you still have R-Mix installed from a previous version of SONAR, try that first. Otherwise industrial-strength spectral-based editing, as offered by Adobe Audition and Steinberg Wavelab, is probably your best option. This allows functionality like removing a kick from a drum part so you can substitute your own, or a cough from a live recording. I'd give a slight edge to Audition but then you have to deal with the whole Adobe rental thing.

Another possibility is that if the percussive sound is short enough, you can cut it and stretch the preceding sound to fill in the gap.

iZotope RX it is amazing for removing things like this.  Train horns click pops and tons of stuff! It will resample from each side near area to cut out and fill in the area with what it thinks belongs there.  Only thing it, is not cheap.
 

Agreed! RX4 is incredible. But it is pricey, so I figured if R Mix could do the job, hey, it's free if you own it. And since it seems like this is a one-off issue, then he could rent Audition for a month and deal with it.

Audition also has a heal feature which may work on that. If you span a pop/click type sound it can sometimes best fit the data on both sides.

FWIW, Adobe CC has a fully functional 30 day trial (or used to), and Creative Suite 2 (which has Adobe Audition 3) can be gotten for free. Most editing tools commonly used exist in that version.

So this is why we should all push Cakewalk along the trail to what seems to be rumoured and the pending Wave Editor. They asked me in the survey so now I'm waiting.. I can only run Wave Lab on one computer and whenever I'm away from home and have my laptop it sucks. Ya I could bring my usb key but I'm scared to death of that thing... 

Cactus Music
So this is why we should all push Cakewalk along the trail to what seems to be rumoured and the pending Wave Editor.

I highly doubt we'd get RX4-level functionality, though...it's a $349 program. 
 
Still curious if R-Mix worked for the OP.