Wrong. Although I suppose it would have a similar effect (slowing down the
playback speed of the deck) it was done by a technique called FLANGING for
a reason.

I have actually done this trick, back in my old college radio days. This
is how it was done on such 1960's classics as Hendrix's "And the God's
Made Love", the Animals' "Sky Pilot" and The Small Faces "Itchycoo Park".

In technical terms, this is called "zero-point flanging". The whole reason
this effect is _called_ "flanging" in the first place will soon be clear.

You need two indentical reel-to-reel master decks. They must be good
quality decks with very low wow-and-flutter, and tweaked to exact i.p.s.
speed. The one's I was using were made by Scully/Metrotech (I can't
remember the model now.)

Make simultaneous copies of the audio track you wish to flange onto the
two decks, using the same tape stock if possible. Set them up for playback
mixed together at the exact same level.

Rewind the two decks and cue them up tight to the start of the track(s).
Now comes the tricky part: you must start the decks simultaneously, and
have the signals be so in sync that they don't "echo" but are tight enough
to cause phase cancellation. Listen for echoing and you'll know right away
if you got it. If you don't hear an _intense_ flanging effect right away
instead of echos you must stop, rewind and start over. I usually managed
to do this manually within about half-a-dozen tries with practice.

Now comes the fun part! Choose one deck and place a fingertip (I used my
thumb) _very_ gently on the FLANGE of the supply reel. This has the effect
of vari-speeding the playback _down_ slightly. You will hear an intense
downward sweep of comb filtering. You must stop dragging the reel _before_
the timing of the two decks slides so far out of sync that the ear
precieves an echo or you'll lose the effect and end up with
Elvis-slapback.

Then touch the flange of the supply reel of the _other_ deck, slowing it
down in turn, and the "flanging" will sweep back UP again. At the point
where the timing converges you'll hear an intense "peak" as the turn-over
point is passed -- and then the effect sweeps back down again.

Continue in this manner, artfully orchestrating the timing of the sweeps
to compliment the music. As in all things, practice makes perfect.

The difference here is that with artificial flanging, a signal is split
into two lines and one of them is delayed and then the two are combined
again. The delay signal is lagged progressively longer, then reversed then
lagged again to produce "sweep".

With zero-point flanging, _both_ signals are vari-speeded _down only_ and
"dovetail" each other producing a far more intense effect, with the
dramatic "peak" as the signals converge and diverge.

Although it's possible to do this using two delay lines and varying them
independently, but to only add more and more delay to the signals (always
slowed down, never brought back up) ends up with your delay lines reaching
their limit somewhat soon.

The effect of doing it with analog tape machines is much more striking.
The tiny imperfections in playback speeds create an ongoing "warm flanging
distortion" (don't know what else to call it) that's very pleasing to the
ear.

One can also use THREE decks to do this trick, but the other tape machine
we had in the studio was an old Crown and it didn't track or sound quite
the same way as the Scullys -- and was _really_ a bitch to start three
decks at once -- you need two people! We only managed to pull it off a few
times but WOW! Now, with remote controls...

Probably someone could do some digital modelling with a DSP system and
come up with something close, but it sure wouldn't have the tactile
sensitivity of doing it the old school way.