How can you evaluate a system with highly processed music?

John Atkinson made the point to Gordon Holt that the sound made by an electric guitar plugged into an amplifier was just as much an acoustic signal as is an acoustic instrument, and he was correct. But recorded sounds produced purely electronically is a different matter: that sound never traveled though air, from an instrument (whether acoustic or amplified) to the recording microphone. There are plenty of recordings in which the electric bass, electric guitar, and/or keyboard instrument/s was/were plugged into the recording console, not into an amplifier and then recorded with a mic.

I’ve watched and listened as a recording engineer played with the dial on a studio’s parametric equalizer (far different from a graphic equalizer), drastically changing the sound of the recording. For evaluating the timbral neutrality of loudspeakers, make and use your own recordings! Listening purely for pleasure is a different activity. "Turn off your mind, relax, and float downstream" as someone once sang. ;-)

@mglik not sure if you have read this old piece.

https://www.stereophile.com/content/capturing-it-live-peter-mcgrath

I was lucky enough to listen one of Peter's recordings recently. Needless to say I almost got tears in my eyes. I'm now also considering upgrading to the Alexia V.

The performance and arrangement are certainly most important.

I do, however, most enjoy acoustic instruments and voices.

Heavily processed Pop, etc. can surely be a lot of fun. And the performance of my system can also be evaluated with any content. 
However, I believe acoustic instruments and vocals are able to be a gauge.

@quattro: I have a bunch of Peter’s recordings, made for Levinson, Audiofon, and Harmonia Mundi. Excellent sound and music.

You can’t evaluate your system’s abilities by playback of electronic and highly produced pop. I found that all my systems can recreate those genres effortlessly. My non-audiophile friends (sounds arrogant of me) always lose their minds when I play something “highly processed” as they experience that emotion that comes with hearing near perfect reproduction of music.. yes, I know that’s subjective….FWIW I’ve found that most of my listening sessions start with electronic music and that after 30 minutes or so I begin to get fatigued. It sounds fantastic initially but I think our brains aren’t suited to long listening sessions with that perfectly articulated sound. If you want to test your system (and acoustics) try a symphony or rock band. Yes, I know the list of variables is endless and subjective and open to fierce debate but these genres will reveal your systems weaknesses much faster than “highly processed” pop/electronic.