I was reading a review of a bass and they mentioned too many "upper harmonic partials" or "high harmonics." What exactly are they? When I play my bass, some notes around the twelfth fret or so give off this odd twittering behind the note itself. Am I experincing these harmonic partials? I am using flatwounds on one bass (Hofner Icon) and roundwounds on a Fender Jazz and they both produce these odd sounds behind the note on certain notes (the Icon produces louder ones). How to rid myself of these? Is it just a part of playing bass and I shouldn't even take note of it? Thanks.