North Korea’s highest political body, the Workers’ Party Congress, is convening Friday for the first time in 36 years. Over the course of the next few days, about 3,000 delegates are expected to endorse the leadership of Kim Jong Un, formalizing a rushed transition of power that followed the death of his father, Kim Jong Il.

In one notable way, the elder Kim was very different from his son.

“[Kim Jong Il] was widely quoted saying that he felt it was best to keep the enemy in the dark. The less he was out there, the less his enemies would have to use against him,” says Jean Lee, an American journalist who opened the Associated Press’ Pyongyang bureau. Much of her time in Pyongyang overlapped with the final years of the late Kim’s rule.

“He never gave a public speech,” Lee says. “There are no recordings of a public speech.”

Despite all the propaganda touting Kim’s achievements, and even video showing him speaking to the public, the sound of Kim Jong Il’s voice was almost never broadcast. There’s only one recorded statement to the masses, according to researcher Curtis Melvin from the U.S.-Korea Institute at Johns Hopkins’ School of Advanced International Studies.

“He uttered one line at a parade, ‘Long live the Korean people’s army,’” Melvin says. “And that’s it.”

South Korean media did once capture Kim’s voice while he made a joke about buckwheat noodles during a summit with the South Korean president. But no public speeches.

Why is Kim Jong Il’s voice so hard to find? He was an omnipresent dictator, after all.

“There’s all sorts of theories about this, I can’t tell you why,” offers Melvin. “But a lot of people said he just didn’t like the attention or didn’t like being scrutinized so much.”

That’s what made journalist Lee’s discovery a few years ago at a museum in northern North Korea so surprising.

“Wandering off in a museum by myself when I spotted this Toshiba TV monitor, with a picture of a painting and a caption saying, ‘Kim Jong Un giving a speech on juche ideology,’” Lee says. “Juche is their philosophy of self-reliance — so of course I pressed the play button on the stand and lo and behold, there was a voice, so I did tape a little bit of that.”

In Lee’s clips, Kim is indeed heard.

“What we’re doing now is trying to find the exact speech,” she says. “Exactly where and when he gave these speeches.”

Lee and her researchers believe it was given in 1974 or in 1980. 1980 is historically important, because 1980 was the last time North Korea held a Party Congress.

Now, Pyongyang is hosting another, in which thousands of the regime’s most trusted insiders are meeting. Kim’s son, Kim Jong Un, who wasn’t even born when the last Congress was held, is expected to cement his authority. To do so, Curtis Melvin says he’ll be heard.

“He’s never been shy to stand in front of people and use his voice,” Melvin says.

A stark contrast to his father. The younger Kim’s public persona is being shaped to appear a lot more like his grandfather — North Korea founder Kim Il Sung, who was known as a gregarious man who mixed often with the people.

“A lot of North Koreans are still nostalgic about the Kim Il Sung era and Kim Jong Un has tried to model himself on his grandfather rather than his father,” Melvin says.

Callbacks to the eldest Kim may be wise, Lee says.

“They want to go back to a happier time in their history. And associate Kim Jong Un with that happier time in their history.”

Haeryun Kang contributed to this story.

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