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

Musical - it has to be an umbrella that covers a whole raft of performance parameters and requires they be within acceptable limits. I think pace, rhythm, and timing come under the musical umbrella but also tonality and timbre. Since it’s hard to describe a “shrill” or bright sounding product that causes listener fatigue as being musical, then high frequency performance is in there too. 
I agree with distortion but I think that’s more of a cause than a symptom.

Unfortunately I think each of us has our own set of these performance priorities that must be met before we consider something to be musical, hence as an adjective it isn’t a lot of use in relaying a performance measurement that can be understood by a community. It’s like saying “I’m pleased with it”.

Unfortunately I think each of us has our own set of these performance priorities that must be met before we consider something to be musical, hence as an adjective it isn’t a lot of use in relaying a performance measurement that can be understood by a community. It’s like saying “I’m pleased with it”.

Exactly!

We have all our own tastes order priorities born from the biases acquired or innate and from our own learning history and from our own system/room limits and knowledege ...

But it does not change the fact that "musicality" must be defined by trained musicians and acousticians working together in experiments when we learned how to control and vary all parameters in an optimal way ...

We learned this way for example how some trained musicians can beat the mathematical computed Fourier limits between time and frequencies perhaps 13 times...Because the ears brain work non linearly and in his own time domain territory trained by evolution for music and speech for social and survival reasons and by professional conscious training ...

Taste there is , but it is not about taste when we use the word "musical" ...

It’s like saying “I’m pleased with it”.

Pleased, until you find something that comes closer to the mark, for example you find out that you can have something be both smoother and more detailed instead of bright and detailed.

Tube products tend to sound smoother than solid state. This is literally what has kept tubes in business the last 60 years after being declared 'obsolete'. The economic facts here cannot be denied- this has kept tube producers like JJ in business. So that means there are enough people out there that are hearing the same things about tubes.

At that point this becomes easier, because all we have to do is sort out why tubes sound smoother than solid state. And that turns out to be the way they make distortion as opposed to how solid state makes distortion.

So we figured, if distortion is the sonic signature of any audio product, then if you built a solid state amp that had a similar distortion product to a tube amp, it should sound like a tube amp. This turned out to be true.

So there's more to this than just taste.

@atmasphere Understood. The ‘distortion product’ isn’t responsible for shaping or determining all of the various parameters that must be satisfied for a product to be considered musical. I don’t think that you are saying that it is, please clarify.

@atmasphere  : E= mc2 : inherited and learned at different levels.

Taste still is as I explainesd. It's my take and I don't read yet any argument that really " beats " it.

R.