Your .spc doesn't even run on my end with the more modern players (and real hardware for that matter) because of one major reason: you failed to set up the instruments. Therefore, all of the instrument pointers are pointing to $FFFF in SPC700 RAM, which is essentially nothing.

Update: Well... maybe not exactly nothing. The player I use by default, Game Music Box, fails to emulate wrap-around to $0000 in SPC700 RAM properly. But it explains exactly why only one sample is playing.

Actually, I think that's just the render if you're talking about the abrupt ending (I myself have no clue). I'm tempted on both this one and epic_caterpillar's entry (I even think they might be the same people) to quite literally create the instrument data myself (just generic instruments with the sample IDs), and then post them here.

we're not same people but both did the same thing

OK. Irregardless of case... I have a bugfixed .spc file: https://app.box.com/s/qaau0trkzdhyz4whlv7o

The render is actually worse than the song because of the missing instrument bug, resulting in all of the samples being the same.

Someone shut that Buvvins up!