Spay for CD

None of which explains OF WHAT magnetism is MADE, but-  "All you need to know is that demagnetizing CDs or LPs improves the sound, or interconnects." and: AMEN(no offence)!  Happy listening!

It’s made of nothing. It’s a force. When you measure magnetic field you measure the strength of the field. You can forget about everything else. When you pull a car with a rope what is the force composed of? Nothing.

So- you’re measuring, "Nothing"? That clears things up. 😬  Keep digging(I love it)!

That’s not what I said. When you pull a car and measure the force what are you measuring? What is it made of? Answers at 11.

Whatever, "field" might be measured, what’s being measured(far as strength), is the field’s energy level. If fields are comprised of, "nothing", rather than energy, E=mc2 is wrong. https://physics.info/energy/ Trying to define it, is another matter, entirely(no pun intended).