Nicely said tmazz. I also use classical music as a tonal reference. But I, and maybe you too, have the advantage of knowing what a live oboe sounds like, so we can use that memory as a reference to compare a recorded oboe.
What can people use for reference if they just don't like classical music, or if they don't know whether the oboe sounds right or not? They "know" the tone of John Lennon's guitar after 40 years of listening to it on dozens of systems. Can that be good enough as an absolute tonal reference?
When I auditioned my current speakers I used a familiar trumpet recording because I am trumpeter. I had listened to it for 35 years on all kinds of (relatively inferior) speakers. It passed the test from my perspective at the time, so I bought the speakers. Now a couple years later, I can hear some of the flaws that I didn't recognize before, subtle things like phase and high Q dips that are hard to hear unless you know what they are and what they sound like. I didn't know how to listen for those back then, nor did I understand the potential weaknesses in crossover design that could cause them. So absolute tonal reference is still dependent on the brain knowing what to listen for and being able to discern extremely minute aberrations. Listening like that is a learned skill, to get out of the music and listen to the sound. It is counterintuitive to the romantic music lover who is easily sucked into the music. It can sound like an oboe but still have minor problems that are easily missed because of the poignancy of the music. The degree of accuracy desired is the question, and that gets into the true accuracy of the recording. Most oboe recordings will be somewhat colored by room acoustics and microphone choice. Like a violin, the recordist will deliberately choose a mic to dumb down this potent sound for mass consumption. But the basic harmonic structure remains intact, it's a fine line. In the end the classical recordings are not perfect tonal references either, unless they are solo instruments in a benign acoustic. In some ways, a singer in a silent recording booth, even with mild reverb effects added is an even better reference than an acoustically recorded instrument.
I use Beatles' "I feel fine" as a reference track both for the unique harmonically rich sound of the guitar intro, and for the crappy old pop song character, which his a challenge for a high end system that is on the knife edge. It is a good test for system smoothness, just like I use a good David Sanborn recording to see just how bad class AB zero crossing distortion is at high volumes.
I think that a relative tonal reference like a distorted guitar can be adopted for accurate system tuning and comparison, if the listener has heard it enough to know what it is supposed to sound like, as an average of systems he has heard it played on in the past, or if he is a guitarist that knows what the subtle tone cues mean, or other special insight to the recording. What do you think?
