Everyone has seen someone hold a microphone too close to a speaker and get feedback. I've been experimenting with pickup feedback on my guitar recently (where the strings don't vibrate, but the guitar still feeds back at loud volumes).
I notice that I can change the position of the guitar and get different tones for the feedback. There seems to be some kind of invisible cone or sphere in the room with various sections that differ in pitch.
Is there any deterministic standard that allows one to know "which notes are where"? It feels like playing a theremin in three dimensions, but I don't have a clear understanding of what pitches will be created at various positions in the room.
Maybe the types of guitars/pedals/amps/speakers create too much variability to know, but I'm curious if anyone is familiar with this.