Bryon, exactly. It’s like using the word ‘blue’ to describe a color. It only gets you in the ball park unless you describe the hue, intensity (value), contrast, gradation etc. in known terms. In my experiences warmth is relative and is dependent on context. To complicate things, as system accuracy improves and smaller differences become larger, not everyone describes these differences in the same absolute terms. A neutral system compared to a sterile system will sound warm(er) and can be described that way as more natural, neutral etc. A system can be neutral but as a requirement must have warmth. Because accurate tone can be difficult to describe, the word warmth is helpful in describing the accuracy of that tone. "The sax was warm and round sounding, as if it were in the room." could be an acceptable statment. Of course the term can also be used to describe a system that is too warm.
Ambient information, or ‘air’, which is key in recreating the recording space is not necessarily the same as warmth. A sterile system can and frequently does have lots of ambient information, but lacks body or warmth.
Recording studios can and usually are 'warm', dead maybe, designed to lack reverberations to control the sound, but not usually characterized as cold. Great pains are taken to control studio acoustics.
All instruments, some more than others have a degree of directionality, so your listening position in relationship to them (distance and direction) will affect the sound perceived. The same is true for microphones. Close miked sources can have more high frequency energy than you would hear from a normal listening position. In addition, the proximity effect of microphones increases bass response of the signal the closer you place a mike to a source like a guitar or vocalist. A lot of singers like this effect as it adds richness to their voices. When you hear a studio singer, you are usually hearing it from the perspective of the singers mouth on your nose (where the mike would be), being played through speakers in front of you. Hardly a 'natural' situation. Instruments, room acoustics, microphone and equipment selection and placement, multi tracking, all manner of tweaking and manipulating the sound after it is captured, and lots more must be accounted for in the recording process to create a recording to give what they hope you consider a natural sounding perspective. In general, its unrealistic to think a recording would ever be heard exactly that way live. Although it’s amazing it works as well as it does...well, sometimes anyway.
