| It is indeed interesting. I'd say that it has to do with: - complex structures (not necessarily always 4/4 or 3/4) - variations in dynamic range (loud parts vs. quiet parts) - storytelling / philosophical themes (the human condition, freedom, suffering, literature) - intense "solos" (Mendelssohn insanely fast yet moving segments on the piano vs. Petrucci going crazy on the guitar) - mastery of musical instruments (particularly true in progressive metal, but metal drummers, guitarists/bassists and keyboard players tend to play at a very high technical level) - song length (like Seventh Wonder's "The Great Escape" at about 30 mins) None of these individually are unique to either genre, but taken together, we can start seeing quite a bit of an overlap. |
Not forgetting a good few borrowing from the folk canon, and I don't just mean late era Rainbow after Ritchie got his new girlfriend. :)