[ 'Nothing', John claims, and Shadow gives him an extremely level and extremely unimpressed look for said claim. Shadow reaches out, picks up his bag, and sets it down directly in front of him. ]

... It's a cassette tape. If you have a tape deck it can play audio recordings, like a a vinyl record would.

[ Assuming John even knows what a vinyl record is. Considering Shadow didn't know CDs until Blake told him, he might not. ]

But if the magnetic tape gets pulled out, you have to wind it back in.