Jazz lovers have new music to groove to from a familiar voice: Ella Fitzgerald’s. However, this music is not new at all. It comes from recordings Fitzgerald made nearly half a century ago.

“I had never heard the tapes. We ordered them up and we couldn’t believe it when we heard what they sounded like,” said music producer Richard Seidel. “There isn’t anything like this. It’s truly unprecedented.”

Back in the early 60s, Fitzgerald performed a series of concerts in Hollywood. During the 12 nights she sang, her manager Norman Granz recorded what turned out to be close to 100 hours of music. According to Verve Music Group, it is one of only two club performances she recorded.

“I’ve worked on a lot of projects, but nothing quite like this,” said Seidel, “What’s so unprecedented about it is that over the course of 10 nights, she did 50 or 60 different songs.”

According to Seidel, most musicians would perform the same handful of songs to make sure their producers had a good take on a particular set of tracks.

With all this music to sift through, Seidel and Universal Music VP Harry Weinger consulted the work of jazz expert Phil Schaap. Schaap had previously reviewed this material in the late 1980s. He confirmed all the music was from the same series of concerts.

Pouring through hours of music from the First Lady of Song, the group compiled more than 70 songs for box set released in time for the holiday season.

But music lovers insist that aside from great music, this new box set adds to the legacy Fitzgerald left behind.

“If one looked at everything she could do in music, she could stand up next to the guys as a musician,” said jazz critic Stanley Crouch. “Everyone knew that. I think that was very important.”

Now generations four decades removed from Fitzgerald’s Hollywood performances will know it too.