Back in the mid 1980s, I thought extreme Metal had enormous potential to accomplish musically much more than it was doing. I was especially interested in the adoption of techniques from Classical music. As time passed, that which I dreamed of gradually became reality during the late 1990s and early 21st Century. Now we have yet another development, not quite what I had envisioned (as I hate the form), but not wholly unrelated to Classical, if we are willing to go back to Aeschylus: musicals. (I say 'if we are willing', because conventionally music predating the 5th Century falls outside the definition of "Classical", and the musical has its roots in ancient Greece.)
Leave it to the Norwegians to pioneer the Black Metal musical. Below is the trailer.