well, i gotta ask. what's going on that you haven't heard before / seem like mistakes in the Mario Bros. 2 Overworld? i presume it's in the first two lines of chords since the rest is pretty standard
what really made my head explode upon a closer listen, there's 2 things actually. when the bass hits the F, F#, G, A thing, that's like the most cliche figure in the world and it's been in 1000s of songs (especially american 'jazz' popular sort of songs from the 1930s and 40s i suppose?) (and also many nintendo games) and the chords are F, Fdim, C/G, A7. it really blew my mind to hear that the A note on the Fdim chord actually had F natural harmonized under it. that was the worst offender. it just HAS to be F#. now, it's easy for me to sit here and complain, but i must admit, from experience, in some cases you may go in and make it what you think it's supposed to be and it just doesn't work. Sometimes you see these paradoxes where the bass will do it the twisty way and the melody will just completely ignore the twists and do it straight, and for some reason it just works fine that way when you breeze through it. it's one of the great mysteries of life. The other issue, which was a little bit less disturbing but yet still defied all norms of the 'genre', is the A7, which in every fiber of instinct feels like it was supposed to be A7, and the harmony note should have been C#, but in reality they used C. this is not nearly as big a 'crime' as the F and A notes over the F# bass, but yet still common sense and experience of the 'genre' still begs that to be A7, at that point in the song. It really makes you want to wonder if there is some technoligical restriction at play, preventing us from having any melody or harmony notes outside the plain C major scale set. but this is disproved if we take a look at the other section, on the D7 chord, we have F#s right in there. The only other thing i MIGHT be inclined to hypothesize is that the melody and harmony line were written and programmed before the bass was there? and it was planned to be less 'jazz' and more 1, 4, 5 triads. then when the bass came along there was somehow a decision to go more 'jazz' and yet the harmony was not changed to match the bass. This is unlikely and doesn't match nintendo's reputation for perfection especially in these types of genres, they usually absolutely nail this stuff. or again to restate my other theory it could simply be that upon trying the 'correct' 'twisty' harmonies there you would expect, it might have just not sounded right. one of the great mysteries of the universe, but sometimes that is the case. BUT, without constructing a sound-alike and testing for myself, my current hypothesis is that it does weaken the song at those moments to have the notes in there the way they currently are, and i do believe it would be stronger if those were sharped. but i am only about 85-90% sure, short of actually constructing a sound-alike and trying it at tempo and in context