@Harumi: Thanks, it's just a silly song from long ago but it didn't have many commands used so there was plenty of room to try out new SNESMod commands. As for recording, it's just the RCA cables from the SNES to my sound card.
@gotoandplay: The times you refer to are filter sweeps (to bandpass filter), this along with the echo volume and feedback are making volume spikes. It shouldn't be that loud though. The mp3 is how it sounds on real hardware and SNES9x, Higan, No$Sns, AudioOverload and SPCTool2 all play the song back without volume spikes (although the echo is a bit more noticeable on SPCTool2 at the times you mention.)
What program are you using to playback the song?