How to overlay two frequency analyses in Logic Pro

yoyoBen,

Thanks for the suggestion. I gave it a try (and managed to get the EQ match curve and re-EQ one track based on the other) but perhaps I haven't described my need properly.

I want to record a guitar test note (eventually more than one...but as separate studies later) directly into the DAW. I then want to send that note through an amp simulator plug in ("amp A") and record the output onto a second audio track ("track A"). I then want to send the same test note through a second amp simulator ("amp B") and record that onto a third track ("track B").

The two tracks ("track A" and "track B") will be/sound different due to the different amp simulators (the result of different overtones generated from the test note by the two simulations). I simply want to visually examine - by superimposing the two spectra - the differences between them...not because I want to re-EQ one to match the other - or generate an EQ curve that converts one to the other - but simply to look for the relative strength of the overtones in each spectra.

Ultimately, if I find a simulator that generates a reasonable set of overtones (i.e. a set of overtones that correspond to a reference tone I'm trying to match from another instrument), I can then work with that simulation to further refine the EQ - (perhaps using Match EQ - or by ear).

The problem is that the various amp simulators - although audibly distinct - all make some sort of approximation to the reference tone...and it is hard for me to "remember" the reference tone accurately enough to identify by ear which simulator is making the closest approximation to the overtones of the reference tone. The graphs would be my "tool" to keep tabs on how a given simulation compares with the reference tone...and perhaps after that, what would need to be done (by EQ) to match the simulation completely to the reference tone...which is where the Match EQ might be very useful. Apologies if I'm not doing a very good job of explaining what I'm after/trying to do - but any assistance in simply "plotting" the spectra of two channels (or more!) on one graph would be much appreciated!

Many thanks for your follow up. I think I found something from Voxengo called SPAN Plus (costs a few dollars but if it does the trick I'm happy to buy the non-free version with the added features). Again yoyoBen, many thanks.

Thanks yoyoBen - was just hoping there was a way to do this within Logic.