Why should we think of "what microphones heard " as a standard

Let me go back to the beginning. The world of music recording is comprised of two, completely separate entities: the audiophile, and the mass market. Audiophile recording engineers evaluate microphones in purist terms---accuracy, etc. Inna, your question is a valid one when speaking of them. But the bulk of your music collection was recorded by engineers with an entirely different approach---using microphones to get a "good" sound, the sound they want. What constitutes good to them? One thing it isn't is literally accurate sound.

The instance I cited above, of micing a snare drum with a Shure SM57, a mic with a presence peak deliberately designed in (the mic is intended for on-stage vocals, where a presence peak makes the singer more audible) is a good example. A mass market recording studio engineer often uses a different mic on each instrument, the sound of the mic used to get a specific sound, one having nothing to do with literal accuracy.

A drumset is often recorded with this collection of mics:

- An Electro-Voice RE20 on the kick

- A Shure SM57 on the snare

- AKG 414's on the toms

- Small diaphragm condenser mics (often Shure or Sony) overhead for cymbals, and on the hi-hat

Each of those mics produces a different recorded sound when used in the same application, the engineer obviously not so much concerned with replicating the actual sound of the drumset, but rather of getting a "commercial" drum sound. I routinely watch an engineer A/B his recording of my drums with a CD of a current hit record, and make adjustments to narrow the gap between the two.

Not only are the mics not used to achieve an accurate recording, the feed from the mixing board is passed through many outboard pieces of outboard electronics on it's way to the recorder. The worst of them imo is the parametric equalizer; when it's adjustment knob is rotated, the sound of the recording is drastically changed, no longer bearing any relationship to the unequalized sound.

It's not simply the microphones whose sound should not be assumed to be providing an accurate recording, but every link in the entire recording chain. The electronics that the sound captured by the mics are passed through are far more responsible for the sound you hear on the vast majority of your LP's, CD's, etc. than are the mics themselves.