How much of these new grad researchers have undergrad degrees in music vs. science or math? I’d suspect there’s very few of the former, and even then they got the position despite their music degree not because of it.
Approximately zero? Could you articulate what exactly you have in mind here?
A liberal arts degree is certainly beneficial to the individual's broader understanding of the world, and I certainly would prefer my elected representatives to have a thorough grasp of history and philosophy, but where is the fundamental research that my everyday life depends on?