Actually, Music is STEM, in the true and classical sense - it's only our perverted modern view that has severed music from its moorings in mathematics.
It was even part of the quadrivium of medieval education: Arithmetic, Geometry, Astronomy, and MUSIC! A classical education not only taught these subjects, but how they were all inextricably interrelated (or intertwingled, as Ted Nelson famously says...)
STEM is not a classical term. Don't go thinking that because we don't follow ancient Greek philosophy or medieval education philosophy that are somehow perverted.
FWIW, I strongly dislike "STEM" as a term because it makes no sense to me in an educational or philosophical sense. I see it more as an attempt to lower the cost of hiring engineers and scientists by increasing the supply. For example, compare the funding going into getting more programmers and EEs, vs. marine biologists and paleontologists, even though all of them are STEM.
To clarify "no sense to me", I despise Pirsig's "Zen and the Art of Motorcycle Maintenance" because of its insistence on a clean division between romantic and classical views. I view "STEM"'s treatment of the rest of the liberal arts as being similarly incorrect in its dichotomous classification. Eg, mathematics is important for the humanities too.
But it's clear what _def is talking about by "STEM", and there's no need to suggest we or modern culture are following along with a perversion because the conversation isn't aligned with your personal views.
It was even part of the quadrivium of medieval education: Arithmetic, Geometry, Astronomy, and MUSIC! A classical education not only taught these subjects, but how they were all inextricably interrelated (or intertwingled, as Ted Nelson famously says...)