Years ago on “That’s Incredible!” (nostalgia, anyone?) I saw a man who “discovered” at a party that he could identify popular recordings by examining the grooves in an LP record. I have my own idea about how he could appear to be doing that, but I wanted to let anyone else share their insight first. (I mean, even with a microscope, can somebody tell what musical piece they are looking at from the record grooves?)
Of course, we all know that there is precisely one groove on each side of the record, right? 
All the sound information on an LP is in fact contained in the groove, so it is at least theoretically possible that someone could do this. My bet is that he could recognize not necessarily the song, but the album. That is, the spaces between songs are easily visible–I don’t know if that’s intentional or a happy circumstance which allows you to find the empty spot on the record so you can easily drop the needle between songs. I would guess that he could see the lengths of the songs (by how far apart the blank spots were) and recognize the album.
check out http://www.snopes2.com
there is a discussion of a guy who could do this for classical recordings.
it takes an encyclopedic knowledge of music, and an ability to spot variations in the groove textures so as to correlate them with a particular piece.
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This is more of a General Question. I’m moving it there.
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Saw an act on the telly years ago, just as schplebordnik describes. It was on a magic show so I was initially sceptical, but assuming it wasn’t a set up, the turn said it was to do with the fact that you can spot the differences between loud and soft passages because there is a physical representation of the music on the vinyl, as opposed to tape or CD etc. where the sounds are encoded in a form invisible to the eye.