Akumajou Densetsu's (CV3 Jap) RC7 chip might be able to produce that song. It's a tough call though, and I'm sure they aren't specifically targeting an RC7 standard for the songs. It is indeed too much for the stock NES sound chip to produce though.
MM9 and MM10 notes: MM10's OST has some tracks that use timings that no NES chip could do. As for graphics, the games didn't use NES standard palette structures either. Megaman 9's boss select screen goes above the limit, and you can notice a 5th palette (at least) in MM10 when you freeze and enemy using the ice weapon.
There are other things too but those are just the more noteworthy examples.