What causes the "pre-echo" you often heard listening to vinyls and elsewhere?

Sometimes you can/could hear the beginning of a track as a very silent "pre-echo", 1-3 seconds long, before the actual loud audio.
What's the cause this phenomenon?

On vinyl, the needle is tracking a groove. And on silent passages or before the song starts, as the record turns the groove next to the one the needle is currently in would have the ridges cut pretty deep and this would be picked up by the needle.  This was especially noticeable if the following groove was loud. 

Same deal on the tape, but with a difference. The tape particles are actually magnetized. As the tape is stored on the reels (open reels or cassette) the magnetism from the  recorded tape will actually have the effect of magnetizing the particles in the tape touching it when it sets for long periods of time.   Old tapes that set for long periods of time will degrade as the magnetism interacts with the layer next to it over time. It's noticeable when playing old tapes. They lack highs and often become muddy sounding as the magnetic particles loose their original strength and alignment.

In an attempt to minimize this, tapes were often stored wound to the end as opposed to re-wound ready for play. This way the ghost was "in the music" and not in the silence at the beginning where it was easily heard. 

Thanks.
Did I understand this correctly: The needle picks the sound in advance like "through the grapevine" , from the next cycle of the groove towards the centre of the disc (through the ridge between the grooves :o/ )?  That would sound logical to me.

I've been aware of tapes copying through, but the vinyls have puzzled me, because I realised copy-through can't be the cause in a fresh record from tapes that have existed only a few weeks.

http://en.wikipedia.org/wiki/Whole_Lotta_Love

[A]t one point there was bleed-through of a previously recorded vocal in the recording of "Whole Lotta Love". It was the middle part where Robert [Plant] screams "Wo-man. You need it." Since we couldn't re-record at that point, I just threw some echo on it to see how it would sound and Jimmy [Page] said "Great! Just leave it."[5]

A prime example of this is Led Zeps "Whole Lotta Love" middle part.

 
I always thought that was an intended effect.

Yes, it works, Dave.  But still, I imagine it was one of those happy accidents that Page just decided to use.

The butthole surfers always swore that the violin on "Creep in the Celler" just happened to be on the tape backwards like that.  I don't know if I believe them, tho it is possible.  Just as it is completely possible Page "manufactured" an early echo after hearing a print through.  Still, both make a better story as told.

@

Yea, Page is one of the great producers.  I've read other tricks he came up with, just not that the pre-echo in WLL was intentional.  I'd love to know - one of my earliest intros into "how did they do that"?

Ah, good one. And a good one for Kramer and Page.