It was actually quite easy to make once I'd figured out the proper way how. I just took a single synthesizer note, applied a 'wah-wah' effect to it, and increased or decreased the speed at which it played in order to make the different notes. You can hear what I'm talking about if you listen carefully: the higher notes seem to reverberate faster, and the lower ones slower, right?

I was actually worried people were gonna accuse me of stealing the actual tune from the Gamecube itself. I'm glad to see that wasn't the case.