This is a rare copy of a recording released by Magickal Childe Books, the imprint of the legendary bookstore. It's narrated by Peter Levenda, one of the editors of the Necronomicon, who appeared in public as "Simon". The tape gives instructions on how to properly use the text.
I should add that I'm not narrator at the beginning. That would be "Frater Ashnook", who ran classes on how to use the Necronomicon online. He's the one who found this and made it available.