I have a question, if I play the natural harmonic at the 5th fret of the b-string and then the 7 fret on the high e-string like this

now these are the same notes, but if I play it with distortion some weird tremolo-like effect occurs,

can anyone explain me why this occurs?
it sounds very cool though
they're probably slightly out of tune, I actually use that effect to tell whether I'm in tune or not.
listen to david collins. that was one of the best replies i've seen on this site.