This is just about the silliest thing I have ever heard. "Demagnetizing tone" - gimme a break! Just how in the heck do you demagnetize copper and silver (your wires, interconnects, etc.), they are not "magnetizable". And, even if they were, how is an audio tone gonna demagnetize them???
Next thing you know, someone will claim that their optical cables are magnetized and need "fixing". Wake up, folks, and stop being so doggone gullible...