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

In a word the fact that musical taste vary as much as the gear choices does not means that the concept of "musicality" is meaningless or purely subjective nor that the experience of "musicality" lack any objective ground ...

Most consumers are ignorant and interpret their blissful ignorance as a freedom of choice according to their fancy , but informed audiophiles, studies acoustics to know what is a "musicality" experience conditions and factors with any piece of gear and in any room at any price ... We go with our brain but also with our wallet ...

Ok i stop and apologize because my "word" is already two paragraphs ... 😁

A good amplifier can be referred to as a musical amplifier. It is not simply a technical term; it expresses how much you love the amplifier.

It's that simple.

In fact, we have our measurement of a good amplifier. If you can continue listening for more than 8 hours, and you still want to listen, that is a good amplifier for you. So, do not judge in a short period of time.

When I think musical I think bouncy and good mid bass. Not necessarily accurate. 

All this sounds simple yet we have many amplifier makers. I suppose most have gotten the "bad" distortion out of their designs, though.

@hilde45 If that were true there would not be a tubes vs transistors debate older than the Internet itself!

Its a bit more complex than that. Many designers don't pay much attention to how the ear/brain system works. So they often just go for the least amount of distortion: your typical solid state amp. Solid state amps have had a reputation since the 1960s of being harsh and bright compared to tubes for the simple reason that the distortion of the solid state amp has unmasked higher ordered harmonics- the source of the harshness and brightness.

Such amps do not tend to get a reputation of being musical and are part of why tubes are still around!