In the early days of recording the goal was to reproduce the music or whatever was being recorded as accurately as possible. Early microphones, wax, and later shellac drums and disks, amplification horns and simple tube circuits were so inadequate, and very expensive, leaving little doubt whether you were listening to a recording or live music. By the 1950s though, the technology began to catch up. Speakers and amplifiers got better, microphones, got better, and perhaps most important, recording materials got better: better lathes, pressed vinyl disks, extremely lightweight diamond needles. If everything was right, it was possible for a recording to win in a real A-B test.
One of the important things that was improved was that vague thing called "presence", which is based on our "ears" ability to place a sound accurately in a 3-D environment. Our ancestors were both hunters and prey, and in such a context, this ability confers huge survival value. So we have a whole bunch of very sophisticated mechanisms, most of which are almost completely instinctual. Most of us cannot describe most of them, but they're there and they use them every day. For example, we use the slight difference in volume of a sound to place it left or right according to how our head is oriented. We use difference in phase to determine whether this sound is close to on axis or how far away from the axis it is, giving us a 3 dimensional effect. We use the pitch of the sound to determine how high it is: low sounds are lower, like rumbling or water, while breaking branches and flapping wings are higher. And the most amazing part is that our brains and ears are doing this in milliseconds, on sounds that may not even have a full wave.
Early studio recordings were as acoustically as quiet as possible. A room with as much sound insulation and damping as possible, so there would be no outside or reflective noise. But as the techniques got better, it didn't take long to realize that something was missing. The most important was reverberation: Every room, even a big outdoor performance arena, has a characteristic echo, and recordings with no echo at all sounded weirdly sterile. The solution was a device called a "spring reverb", which was a speaker and microphone connected to a short piece of spring, which would transmit sounds more slowly than air and could be adjusted fairly easily to produce a desired amount of echo. Nowadays the same thing is done with digital electronics.
Next came stereo. Two microphones were used in live situations and mixdowns to two tracks in studio situations to simulate the volume and phase difference that we use to detect position. Attempts were made to do even better with 4 and more channels, but it turns out that they were getting into diminishing returns. Some of these things still exist but they are mostly used for things like movie sound effects, so the rumbling or TIE fighter or whatever seems to be coming from behind you.
When the CD came along, one of the hobbies of audiophiles was to set up A-B tests between identical recordings on both CD and vinyl. I participated in several. With brand new vinyl and good equipment it was hard to tell. Once the record had been played a dozen times or so, it was easy. There were occasional scratches and pops, and there was a constant background hiss.
The way a stereo record is recorded, the lathe's cutter has two axes, each 45 degrees from the plane of the record and 90 degrees from each other. A sound that's only to come from one speaker makes oscillations only on one, leaving the other stationary, and vice versa. Since most sounds will come from both, this is mostly a 3 dimensional groove.
Imagine what happens when something happens to one of these tiny groves: a mote of dust lands on it, or a tiny scratch forms: the needle is deflected slightly from where it's supposed to be. It's unlikely that this will be in perfect stereo phase so our animal brain puts it some random place in the sound field. It's not even a full wave, so we don't actually register it. Another comes along a few milliseconds later and we do the same thing at a different random place. Our animal brain decides that whatever it is that's producing all of this has some size, and isn't just two disembodied speakers, but is present in the room.
CDs are unaffected by dust or scratches (at least within the limits) so they initially sounded sterile. It isn't hard to synthesize "presence" though: just add a tiny amount 3D white noise.
addenda 27 Oct 2017
A lot of guitar amplifiers have a control called "presence", which slightly changes the equalization, boosting the upper midrange. On some amps, this also includes some negative feedback for that range, which reduces distortion there, which are the fundamental pitch of the guitar are, but leaves (intentional) distortion alone across the rest of the spectrum--including white noise and the higher harmonics.
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