Rising sound

[Panopticon]

I am familiar with this effect as a result of playing the guitar. The only reason the two notes sound different in that test is because of the scale between them....I have written a song that has a guitar part that goes, for example, G2 F2 E2 D2 G1 (where all of these are played as power chords with an octave doubler). Since a guitar doesn't go low enough to play the last power chord, I just repeat the first one, but in the song it sounds lower than the preceding four chords. Also, this only works with the octave-doubler, if I just play single notes or two-note power chords, the last G doesn't sound an octave lower....