No, you can't boil them (well, you could, but they would be ruined in the process).
The sounds they conveyed when your brother used them were transitory;
once he stopped using them, they were no longer under either
his influence or that of the content of what he was listening to.
You need to get a grip on reality.
Evil does not come from or through any music, no matter what the message.
It cannot and does not become part of any inanimate object through which it passes.
I like what Steven Weinberg said:
"With or without religion, good people can do good,
and evil people can do evil, but for good people to do evil
--- that takes religion."
Be careful what you believe and what you think.
At best, most of it will either remain with you at all times
or come back to haunt you later.