I've been testing Trackspacer, controlling the full instrument mix from the lead vocal. In theory, this should make the vocal stand out better without actually turning it up. And it does do that, but at the same time just sucks the life out of the instruments during the vocal.
To be fair, I'm trying this on a finished mix where I've already created a spectral hole for the vocal and used automation to drop the instruments slightly during the vocal phrases and bringing them up in between vocal clips. IOW, where I've already manually done what Trackspacer purports to automate. Consequently, I'd expect the results to be underwhelming.
I can mitigate the life-sucking action a little by tweaking Trackspacer's LP and HP filters. There is a passage in the song that's just a lead vocal over bass and drums. The drums are big during that section, featuring heavy toms. In order to keep Trackspacer from thinning the drums out too much, I raised the HPF so that the < 600Hz content of the vocal would not effect them. Unfortunately, that had the effect of making the vocal more sibilant, because only the higher frequencies were being unmasked by the plugin. Catch-22.
I can also mitigate the negative effects by simply turning down the % control on Trackspacer, reducing the amount of gain reduction. The more subtle the effect, the less damage it does. However, to my ear the best sound was when I turned it off altogether.
I'm still experimenting, but my initial reaction is that conventional EQ and automation will give you far greater control and more desirable results than this plugin can achieve.
The market for Trackspacer, however, may not be people like me: hobbyists who can take all the time they need to tweak a mix. More likely, it will appeal to folks like yorolpal, who crank out material in bulk and must work within strict deadlines. It could be a time-saver for them. Unfortunately, the bulk of Trackspacer sales will probably go to hobbyists who are hoping for a shortcut around having to learn how to mix, and they'll be disappointed.