It may be the most famous 18.5 minutes of silence in U.S. history, and it's one of the last great mysteries of the scandal.
But CBS News Correspondent Eric Engberg reports, some audio experts met Thursday at the National Archives to consider the possibility of retrieving what was said.
The tapes that brought down Richard Nixons presidency are all treated as historical treasures in their protected vaults at the Archives.
But it's tape number 342 that still generates mystery.
Its the one with a missing portion of the conversation between Mr. Nixon and his top aide, Bob Haldeman in their first White House meeting after the Watergate burglary.
And just what did the experts have to say about the chances of retrieving those missing words? They were not very optimistic.
"If you dont hear anything, theres no reason to believe theres any hope of processing or finding something," said John McKnight of Magnetic Reference Laboratory.
And former FBI official Bruce Koenig sounded the same tone. "Even if somehow you recovered one-tenth of one-percent, the end product would be that it is still unintelligible."
But noting that amazing technological advances are on the horizon, the experts were careful not to rule out all hope. "I cant imagine that I could not extract something. Just what is not known," said Steve St. Croix, an expert in sound restoration.
At a government lab in Colorado, there are computers which provide the hope of someday being able to erase an erasure. Scientists there can get a clearer picture of a signal on a magnetic tape than was once possible. It might be possible to build "voice maps" that could render actual words.
"We have shown promising results that, if there is some scrap of a recording left, if they haven't done a good job or something like that, then you might be able to get something back," said David Pappas of the Commerce Department's National Institute of Standards and Technology.
In the meantime, the expert panel had an interesting suggestion. Using Nixon era machines, they recommended recording some new tapes and erasing them, then giving a shot at recovering the erasures to anyone who wants to try.
And if someone should surprise everyone by accomplishing that feat, they'd get a crack at the 18.5-minute gap.