if music was solvable then the most skilled people would systematically...

Music is like the other "squishy" problems, defined by gatekeepers who don't have fixed or knowable criteria for success - they "know it when they see it" and the target moves depending on their moods - inputs that range from the gatekeepers' own personal history through their recent experiences. Nobody can really "win" these fields without the gatekeepers permitting it to happen, and no matter how well man, woman or machine may think they know the gatekeepers' criteria, they can pivot on a whim.

Then there's the age-old criteria of the casting couch - which LLMs won't be achieving any time soon, at least not without appealing sex-bot embodiments.