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

Clearly, you and others have discovered there is a widespread predilection for 2nd and 3rd order harmonics, and there is a predilection for sugar, fat, and salt, too. But all of those preferences could be changed by changes in taste

@hilde45 How we see things, and how reality really is are usually two different things.

Emphasis added, to the part that is a false conclusion. The only way for it to be true would be to somehow modify how your ear/brain system detects sound, and we're not there yet- give it a hundred years and we'll see 😉

In the meantime we are stuck with human hearing perceptual rules which are surprisingly consistent from person to person unlike taste buds. That is why, for example, we can use a dB scale on VU meters. Also for example why mp3s were even possible (they rely on the masking principle of the ear). Masking, BTW, is an essential bit of what I mentioned about distortion above.

Its easy to prove with very simple test equipment that the ear uses higher ordered harmonics to sense sound pressure, and that they are assigned 'harsh and bright' by the ear. This isn't something for debate, its something you learn about in school.

The musical nature of the 2nd harmonic has been known longer than electronics. That higher harmonics are not acceptable in the audio presentation has also been known for a very long time: I refer you to the Radiotron Designer's Guide, 3rd edition, published in the 1930s. Human ears have seen no significant evolution since then, although taste has certainly changed. 

Getting what the difference is between hearing and taste is what this is about. Designing something to be musical is all about understanding how the ear perceives sound and not at all about the taste people express.

If you want to talk about the taste people express and relate it to audio design, you'll be participating in one of the larger myths in audio- that of a certain audio product being better at one genre of music than another (the absolute classic example of that being a JBL L-100 being better at rock than anything else, which is simply silly). In reality, there's no known way of designing any audio product to favor a certain genre. If there were, there'd be classes on that topic in colleges and universities.

Enlightening discussion on “Musical” in terms of amplifiers 🤔.  Yikes…if I could only figure out Liquid, Bloom, Veiled, and Rolled-off😳

My definition is simple … and, yes it’s my interpretation. 
If you get engrossed in the music such that  you don’t think about the sound, clarity, detail, slam, <insert your favorite audiophile adjective>, etc … just the music, that’s musical in my book. 

and yet, surprisingly not every ear brain is a fan of a well played Strad….

there are outliers @atmasphere ….. thankfully devolved as they might be….few

I used to read here on Audiogon about all of the descriptive high-sounding adjectives to describe the sounds coming from a system....’soundstage’, ’layering’, ’decay’, ’imaging’, ’slam’, ’attack’, 'front-to-back', ’height and width’, ’PRAT’, ’air’, ’deeper bass’, ’sweet spot’, etc. .............and in the beginning, I thought it was a bunch of hogwash. But, as I moved up the hifi food chain, all of those adjectives made themselves known and very apparent to me one by one without anyone having to explain it to me. I knew what each one was immediately the first time I heard them. Some of the adjectives upon hearing them the first time was almost like a religious experience....and I kept throwing money at the hobby as faithfully as a religious person pays tithes. In other words, you’ll know it when you hear it...and you’ll miss it when or if it leaves your system.

After all that, I am still unable to explain those adjectives to a nonaudiophile.

....you’ll immediatley know what it is when you hear it.