For years, jazz experts have known about a priceless recording of a 1957 concert at Carnegie Hall in New York City, featuring some of the biggest names in jazz, including a rare performance of the Thelonious Monk Quartet with John Coltrane. The Voice of America taped the concert for Willis Conover's worldwide jazz program, but it was later filed away and forgotten. So what ever happened to these much sought-after tapes?

It was known as the "Holy Grail of Jazz," a collection of tapes that contained one of the most important performances in modern music. The benefit concert from November 29, 1957, was an all-star event starring Billie Holiday, Dizzy Gillespie, Ray Charles, Sonny Rollins and Chet Baker with the Zoot Sims Quartet. But it was the hour-long performance of the Thelonious Monk Quartet with saxophonist John Coltrane that fans were longing to hear, especially the Library of Congress' recording lab supervisor Larry Appelbaum.

Larry Appelbaum holds very rare previously unpublished live recording of the Thelonious Monk Quartet with John Coltrane, at the Library of Congress in Washington

Earlier this year, Appelaum's wish came true when he accidentally found the tapes while digitizing Voice of America audio materials that had come to the Library for preservation. He says finding the tapes was an important discovery, mainly because of their historical significance.

"The tapes are physically in good condition, they were recorded well, and the performance is so terrific," he said. "And that is what I think is exciting everyone the most, is that this is one of the most important groups in post-war jazz."

Levine: I remember the '50s in jazz as being a great period. Would you say that that was a great period for both Coltrane and Monk?

Appelbaum: I would. Monk and Coltrane working together. Monk was active once again and experiencing a new level of creativity. Coltrane was really blossoming. He had put his health problems behind him and he was really breaking free of a lot of the conventions of be-bop and past styles. So the two of them worked extremely well together.

Levine: Is this just the beginning of maybe a run of other discoveries? Do you think there are more gems to be found?

Appelbaum: There are certainly more gems. I don't know if it's more gems like this. There's very little that would be considered a "holy grail," at least for jazz collectors. But yes, there's a lot of terrific material here, and there's always more.

Blue Note Records was the top bidder for the tapes and recently released for the first time on CD, Thelonious Monk Quartet with John Coltrane at Carnegie Hall.