What is meant exactly by the description 'more musical'?

It's a subjective descriptor. It means that the whole of the component's sound conveys music in a way that pleases. Or a way that conveys the emotional content of the music. It's the most important descriptor. It is my bottom line when evaluating a component. 

Musicality is more related to the sound from the perspective of the gear in the mind of the average consumers ...

But in reality any gear experience evaluation AT LAST is conditioned by the relation between this gear system synergetical or not as chosen and the room acoustic ...( it is even conditioned by the mechanical embeddings working dimension ( vibrations/resonance) and also the electrical embeddings which is mostly the electrical noise floor level of the system/house) ...

Then i prefer the term immersiveness instead of musicality alone , it implicate the listener engulfed in the acoustic space of the recording himself , included in it or part of it with his own brain and room ...

But the real meaning of musicality acoustically speaking and out of any marketing vocabulary cover two aspects of sound related to two acoustics concepts , the timbre experience and the immersiveness experience which immersiveness is related to the ratio of the listener envelopment concept ( LV) in acoustic and his dual concept of the location and width of the sound source ( ASW) .

 Then musicality is an objective acoustic concept which we can control from inside the gear and from the room and from the relation between the two ...This objective concept and his related set of controls instances  can be measured in many ways and also subjectively evaluated ...

@brianlucey  is right to say,

"Musical is a qualitative term not a quantitative measure."

This is right. I'd only add that the presence of quality in our experience can be causally linked to our environment. In this respect, the quantitative measurements of science can help predict when we will experience a quality. (See the example about a 'red' stoplight, below.) But they fall short of fully explaining why we arrive at our qualitative judgments because those involve our qualitative preferences and goals. 

@atmasphere

Thank you for your reply. It’s excellent pushback on what I wrote. You have made me more uncertain about my position and I need to think about it a bit more. Thank you for taking the time to unsettle me.

I’ve become uncertain about what question is at stake, now. Your last post said, "Taste is entirely different. No accounting for it."

I thought that’s what we were debating -- whether the word "musical" (a "taste"" word) is one which scientific measurements can determine.

Let me recap where I think we’ve wound up.

• The question, I thought was, "What makes a piece of audio equipment sound ’musical’"?
• I thought your answer was something like, "We know what does this. It’s XYZ physical laws plus ABC physiological facts."
• I replied that scientific answers can only partially explain what "musical" means other factors can enter into what "musical" means.
• These would include cultural factors -- personal taste, previous experience, and social context -- to name just a few.
• [N.B. I didn’t say science couldn’t help. Nor did I say that everything was interpretation, or "whim" (your word). Some things are settled by scientific conclusions, but not enough to establish what "musical" means.]

So far so good?

You are now replying that if I lose my keys in my house, my perception won’t change that fact. Or that I must stop when the traffic light is "red."

Such examples betray a tactic. They would substitute simple and obvious cases for complex and fuzzy ones. "Where are my keys?" is a categorically different problem than "What makes an audio component(s) ’musical’?" Why? because the keys question is straightforward -- because it has well-understood parameters. The nature of the question and answer are bounded by well-established conventions, past practices, and simple goals. There is not a wide range of meanings for what it means to "find keys." What it means to "find love" is much more in doubt; what it means for a system to be musical is also fuzzier. Those examples are not straightforward; their conventions, past practices, and goals are not settled. Nor can science settle them.

So, your keys example works for your argument by implying that that fuzzy cases -- like what "musical" means -- is the same as easy cases. Not really a fair example. You might as well say that the rules of soccer are as simple and clear as the rules of chess. The rules of chess are stipulated and determinative in a way that the rules of soccer cannot be. The word "musical" is more fuzzy, by nature; more like a "game". Not all words are bounded by rules, though. In some cases the meaning of a term is only partially captured by scientific language -- then it must open out to the various forms of life in which it becomes meaningful.

My previous reply tried to offer some common ground to your position. You did not give me credit for it. I said,

I would agree with you (and science) on this, only: that "taste" outside of the lab is often too wild, too unregulated in procedure, too unstable in judgment to be reliable. That’s fair. Where I disagree is that the scientist/engineer somehow can "anchor" laws of perception in reality in a way that is capable of correcting interpretative judgment. If someone hears a 2nd order harmonic as unpleasant, would they be wrong? No, what we’d say is that some people are not "wired" to enjoy the 2nd harmonic -- just as some people are "wired" to dislike even mildly spicy food.

But I put the word "wired" in quotes because it’s really a misleading (because physicalist) word. It’s not really wiring at all. Rather, there is a complete system of human physiology, habituated expectation, and linguistic training at work, here. These include what seems to be only the "last" node, the listener (or eater). What some scientists get wrong is that the listener doesn’t just receive a stimulus (a 2nd order harmonic) and then have a response (pleasure); rather, every listener approaches a stimulus with previous experiences that condition how the stimulus is received. There is a circuit at work which includes the context, past and present, of the listener. That includes their wants, needs, desires, expectations at the level of meaning and interpretation.

Is there a correlation between 2nd harmonics and the way we measure the brain? Sure. Just as there is between the chemical composition of sugar and the taste buds -- and the sections of the brain which register "sweetness." But preference for sweetness also requires habituation in conduct; one can habituate to dislike sweetness and other "natural" preferences. Often, how one is raised plays a role, here. (Cf. Bourdieu on habitus.) The brain is a plastic instrument.

To repeat what I said at the top, here -- we may be missing each other because we are not really clear about the issue we’re debating. I may be the one who has blurred things. If so, I apologize.

I feel that this is what is lacking in my system right now, and I am cycling through preamps in search of the right sound. I am trying to stay with solid state as it fits my lifestyle, but I may have venture into the tube world. I will know it when I hear it. 

My summation: INVOLVING. Takes your full attention, pulls you into magical moments (to a greater or lesser degree).

1st, an involving performance: composition, music and/or words, musicians, recording skills, engineering skills, production skills, puts a terrifically involving product in your hands

Now: total system: produces excellent Involvement?

Next: evaluate a change of something: equally involving? surprisingly more involving?

Verify the change is real (nothing errantly changed during the gear switch); buy it!