Bob,

This does look nice - I like the aspect of it that it will automatically overlay 2nd, 3rd, 4th instances of the plugin so you can do some comparisons. For pay, you can do something similar with Har-Bal except that it will also create an FIR filter to make up the differences between the two files being compared. It's a great way to quickly EQ a track that you want to sound like a similar track. Craig Anderton did a writeup on it a couple years ago in either EQ or Electronic Musician.

I've downloaded it to give it a whirl.

Another one that you might want to check out is a narrow-band analyzer with somewhat similar function - BlueCat's freqanalyst.
http://www.bluecataudio.com/Products/Product_FreqAnalyst/

This one has an opacity control on the GUI and you can stack one on top of the other to do a similar thing as with the one you show here, but a little more tedious. I've got to give the one you linked a whirl. Couple it with a linear phase graphic EQ and dial-in that tune!!!

-Scott

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