From August 1971 until July 1973, a voice-automated recording system that was known to only a handful of people in Richard Nixon’s White House picked up virtually every word said in the Oval Office.

Ken Hughes, a researcher at the Miller Center’s Presidential Recordings Program at the University of Virginia and author of Chasing Shadows: The Nixon Tapes, the Chennault Affair, and the Origins of Watergate, has spent the last decade listening to, transcribing, and analyzing hundreds of hours of the Nixon tapes.

Hughes spoke to The Daily Beast about how the tapes became public, what’s on them, and the best places to listen to them online.

Can you walk me through how these tapes became public and why some are just now getting released nearly 40 years after they were recorded?

Nixon lost control of them in ’74 because it became criminal evidence in the Watergate investigations, so they were no longer under his control then. He tried to regain control over them, and the Ford administration almost let him take all the tapes in an agreement that would have let him destroy them, which would have been a dire loss to history. Fortunately, Congress intervened and said these tapes are public property. Congress also passed the Presidential Records Act, which says that all the records of future presidents from that time forward belong to the people and not to the individual presidents.

Nixon nonetheless continued to fight until the day he died to prevent the American people from ever hearing what was on the rest of the tapes. Some of the Watergate recordings had come out before his death. After he died, the government started a systematic review and release process beginning with the abuse-of-power tapes in 1996, and there are 201 hours of them.

Then the Archives started the chronological release, which covers February 1971 to July 1973. A batch came out in the ’90s. Then there were five subsequent releases that only came to a conclusion in August 2013 when the April-through-July-1973 tapes became public. So the official number now from the National Archives is 2,658 hours of Nixon tapes that have been declassified.

What has your experience listening to them been like?

To me, this is almost like having a time machine. You get to actually hear what really happened during this incredibly eventful 30-month period—not only in the Nixon administration, but in American history. This is when Nixon engineers the diplomatic opening to China. It’s when he negotiates the first strategic arms limitations treaty. It’s when he engineers the U.S. military exit from Vietnam. And when he wins reelection in a landslide, which was a realigning election in American politics that changed the dominant coalition from the liberal New Deal coalition that had prevailed since Franklin Roosevelt to a conservative Republican coalition that dominated presidential politics through the end of the Cold War. And this was all at the time of Watergate.

For people who love history, this is a once-in-a-lifetime, once-in-history resource.

For the tapes that were released in the 1990s, did you have to go to the National Archives and listen to them? Did you buy the tapes?

At first, in 1996 and 1997, I had to go to the National Archives. We would get a sheaf of papers and pencils and listen to the tapes. Everybody who wanted to listen to the tapes had to go to a National Archives and listen to them there.

Could historians and journalists make copies of those tapes in the ’90s?

I’m sure you have seen Stanley Kutler’s Abuse of Power: The New Nixon Tapes that came out in 1997. That was based on the tapes that came out in ‘96. Stanley did the best job possible at the time working under very severe limits. He was at the Archives himself; he couldn’t work at home.

Is that book in the form of transcripts or narrative?

It’s in the form of transcripts with some explanatory texts.

How did the National Archives release tapes after the batch in the late ’90s?

The Archives made it possible for us to get copies of these tapes so that we didn’t have to physically go to the Archives to listen to them. People like me could work on them at our offices instead of having to trek out to College Park to listen to them every day. [One of the largest repositories of the National Archives is located in College Park, Md.]

When was this?

I don’t remember exactly—’99 or 2000.

So you could buy versions on audio cassettes for a particular period?

I don’t think we bought them. I think the Archives allowed us to come in and make copies, but I just don’t remember. Other libraries like the JFK Library would let you buy tapes by mail.

The next thing that happened, which was really great, was that the tapes became available on compact discs. This was a big step forward in the technology because we historians got to listen to the same quality of recording that the archivists were using themselves. These were digital duplicates of the original analog tapes, so the sound quality was much better than on the cassettes. And we could make copies of these digital files on our computers and transcribe anywhere anytime we wanted.

And apply audio filters to make the sound easier to hear.

Exactly. We could start using all the things that digital software apps can do to make these recordings easier to understand.

Was there a long lag between those tapes and the tapes released more recently?

They’ve been coming out in batches every few years. It has been a process of two decades from the ’90s to last year to complete the release. That’s because basically all the agencies of the federal government that have to do with national security had to listen to the foreign policy conversations and sign off on them before they could be released. While it was a very long process, it was not an unjustifiably long process.

What’s the total number of hours of tapes—3,700?

That’s the number we had been using for years. I went back and checked that for my book, and we calculated 3,432 [hours]. I checked that with Cary McStay, who’s a Nixon expert at the National Archives. Of that, 2,658 hours have been released.

What does the Miller Center do with regard to the Nixon tapes?

Back in the ’90s, the Miller Center started a presidential recordings program to study the secret White House tapes of presidents who had recorded them. The first project was the Kennedy tapes having to do with the Cuban Missile Crisis. What the Miller Center does is use scholars who are experts in the era of these presidencies to give multiple reviews of transcripts, each scholar trying to correct errors to have the most accurate final transcript to give the public.

While these tapes are all public domain and every American who wants to listen to them can listen to them, they’re also really difficult. Without a transcript, it’s incredibly difficult to navigate through them. The Miller Center has been releasing transcripts—first as books and now as digital editions online since that’s how most people do research—so that people can have accurate, authoritative transcripts to refer to while they continue to use the tapes as the definitive resource.

The Nixon part of that started in 2000 when they hired me to listen to the Nixon tapes from the beginning. I started with February 16, 1971—the first day of taping—listened to all the ones that I could, and summarized what is said on the tapes. So I got to listen to two straight months of the Nixon administration from mid-February to mid-April of 1971, and it was fascinating. It was like starting a new job; you don’t know what the people around you are talking about for the first few weeks, and after a short time passes, you start to learn everybody’s shorthand, and then it becomes very easy to understand.

I’m sure there’s a very Truman Show aspect where you’re getting everything—time-important stuff and the minutia—and only over the longer period does it become clear what you have, I assume.

Exactly. There’s the president discussing a salute to agriculture with poster children and things like that, but he’s also coming up with a strategy for extricating the U.S. from the Vietnam War and learning bits and pieces about how China is responding to the diplomatic opening. It’s really fascinating to listen to these things develop in real time.

Are all of the clips that have been released available now online?

Yes. We have the digital files for basically all the president’s tapes—particularly the Kennedy, Johnson, and Nixon tapes. You can go to our website and download them for free. On our website, the Nixon tapes go up through, I think, October of 1972. Then, through July 1973, you can get those through the Nixon Library website, which are also free.

What about the transcripts side-by-side with the audio?

The transcripts are a different matter because the government never allocated money to make transcripts of these tapes before they declassified them, so that has been left up to the public.

So are you making partial transcripts or comprehensive transcripts of particular periods?

We’re making transcripts to the extent that we have the resources to do so. It’s an expensive process since we have multiple scholars reviewing each transcript. We’re putting a lot of transcripts online for Chasing Shadows.

Editors Note: A previous version of this article incorrectly stated there was 120 hours of tape, and has been updated to reflect 201 hours.