SPRING VALLEY, N.Y. One of Washington's greatest unsolved mysteries sits inside a vault at the National Archives in College Park, Md., forever suspended at a temperature of 18.3 degrees and 40-per-cent humidity. It is Tape 342, Richard Nixon's secret reel-to-reel Watergate recording, and it contains the infamous 18½-minute gap of silence.
For more than 30 years, historians and Watergate junkies have wondered what Mr. Nixon said in those unguarded moments, and why someone, perhaps even the president himself, felt it necessary to erase those conversations from June 20, 1972 -- just three days after the break-in at the Democratic National Headquarters.
Although it has been played just a half-dozen times since then, countless people have listened to copies of the 18½ minutes of hum, fruitlessly hoping to hear voices hidden beneath the white noise.
The National Archives has mounted a high-tech assault to try to recover the missing conversation between Mr. Nixon and aide H. R. Haldeman.
They hope that modern technology will be able to reveal the tape's mysteries.
"This is like looking for extraterrestrial life," said Paul Ginsberg, an audio sleuth who is one of a handful of people being given a chance to try to end the silence. "I call this audio archeology."
Mr. Ginsberg, 56, works from his "tape cave" -- a windowless room in the basement of his home in Spring Valley, a village about a 45-minute drive up the Hudson from Manhattan.
A life-long audiophile, he seems to have kept almost every old tape recorder or audio gizmo he's come across.
One shelf holds a machine that scrambled telephone conversations; another holds a Nagra SNS -- the same tape recorder you see burning up on every episode of Mission Impossible. It was the best you could buy at one point in the 1970s.
"I weep every time I see them burn one of those babies up," he said, his laser-blue eyes flashing. "Those are beautiful little machines."
He then pulled out his "baby": the TC-880B. It's the exact same model of the Sony machine that Mr. Nixon used to secretly tape the White House conversations.
It may be key in solving the tape-gap mystery.
Mr. Ginsberg can carefully monitor the vintage recorder's electronic signatures, then use them when playing back the tape on a modern 60-channel machine to enable him to break down what's on the tape, piece by piece.
The subject of the conversation on the tape is an enduring political mystery.
Some have speculated that Mr. Nixon may have clearly outlined the conspiracy. Or it may be simply that his conversation, captured on other Watergate tapes where he rails against political enemies and suggests hush money to end the scandal, is even more unflattering to his image.
Given Tape 342's obvious historical importance and its fragility, the National Archives isn't allowing anyone to experiment with the original yet.
But Mr. Ginsberg is already well known for his work with the Central Intelligence Agency and Federal Bureau of Investigation, which includes the enhancement of FBI tapes from the Branch Davidian standoff in Waco, Tex. And on a test tape that replicates the original, he has been able to identify six separate channels of audio signal -- an encouraging result.
Mr. Ginsberg hopes to find a technical glitch from when the tapes were erased: a dust particle or a tiny malfunction in the tape heads that may have left a residue of conversation. "You've got to go really deep into the tape," he explained.
"But I'm ready for this. My heroes are Thomas Edison and Sherlock Holmes. I don't give up."
His detective work hasn't received a lot of publicity, at least not yet. But it is being watched closely in some circles. Wired Magazine recently devoted a major article to the effort.
Another audio detective selected to work on the project is former FBI surveillance expert James Reames. He told the magazine that he'd use the same sort of technology that reads computer hard drives to see if he can uncover a "sliver track" of speech that then might be digitally enhanced.
Mr. Reames told the magazine that he might even be able to find fingerprints on the tape -- perhaps even Mr. Nixon's, which could lay to rest the question of whether the president directly handled them. Although the official version was that it was Mr. Nixon's secretary and it could have been any number of aides, many believe that the president himself erased the tapes -- including director Oliver Stone, who depicted him doing so in his film Nixon.
"We'd take any of his 10 fingers," Mr. Reames told Wired.
But the greatest challenge with Tape 342 might simply be ensuring that none of the fiddling causes lasting damage. One of the archives' greatest fears is the same thing that everyone who has ever pushed the button of a cassette recorder knows all too well: eating the tape.
The archives likely won't select its candidate until next year at the earliest.
But if he's chosen, Mr. Ginsberg said, damaging the tape would be his nightmare.
"My suicide would follow directly thereafter," he said.