Writing from the POV of an engineer, I assert that what you hear in that recording is not feedback, it’s sympathetic vibration with a soupçon of resonance.
[Editorial aside: take with a big grain of salt most of what you read on wikipedia. Nearly anybody can put nearly anything in there. A professor of literature illustrated my opinion of it nicely in an interview saying that he read a wikipedia article cited by a student and found three easily verifiable errors of fact. The subject of the article was specific to his field of expertise so he logged in, corrected the errors, adding appropriate citations, and ignited a two or three week firestorm of tribal lore, mis-statement and misunderstanding. When it quieted down there were not three errors, there were nine. He accepts NO wikipedia citations in any work he assigns.]