Oooooh! I think I can help for once!
Okay, here we go, here is everything wrong with the nsf file that I can find.
Tracks 1-4 are blank.
5 is perfect but I think it's supposed to be a diffrent song and happen to come out strange like this. Very strange! I'm almost sure it's the Mars level music, but it doesn't sound anything like it.
Track 6 is something strange indeed! I don't even recongize it!
I think it matches up with Track 5...
About this time, I got an error about canvas drawing while rappidly switching tracks like a moron. I think I overloaded the NSF player. Trying it again...
Track 7 sounds like a sped up distorted version of 16...
Track 8 attempts to fix itself, it starts off BLAZINGLY fast but then part of it slows down to it's correct speed but only one part, Square 2.
Track 9 is perfect in speed, but all the instruments are off beat from one another and they stop and start randomly sometimes I think.
Track 10 is a weirdly distorted version of 5. Trippy.
11 is the main theme but the square waves are off beat from the rest of it (Triangle and Noise) which is perfect.
12 is a perfect Snake... at least it sounds like it... I might be wrong on that.
Track 13 is VERY close to the original, just sounds weird and distorted. The level is called Amazon if you want to check it out.
On 14, the only thing wrong with it is the noise is off beat.
15 is 14 without the noise and it's perfect.
16 is dead on perfect
17-20 are AWFUL. I think they're distorted songs.
21 is the dying noise... it stops abrubtly.
22 is just a jingle but it's perfect too.
23 to 68 is all sound effects. There are a few gaps where there are no sounds in the track.
From there on they're all blank.

Maybe that can help someone figure out what's wrong if they've never played the game. ^_^