The Beatles went viral before there was viral.

In 1964, after playing to a staggering 45% of American households on “The Ed Sullivan Show” in February, the band embarked upon a chaotic tour of North America in August. The dates were highlighted by a legendary Aug. 23 show at the Hollywood Bowl in Los Angeles, 60 years ago today.

“It's hard to understand how it was before the internet, but there was a thing called word of mouth,” says Beatles historian Martin Lewis, who will mark the anniversary with a discussion Friday at The Philosophical Research Society. “The Beatles became successful because friends told friends. They said, 'Have you heard this? It's astonishing.'”

USA TODAY recently spoke with Lewis for The Excerpt podcast (available Aug. 25) about how The Beatles went from being virtually unknown in the U.S. in 1963 to global icons in 1964. Here are a few highlights from his conversation with Dana Taylor (edited for length and clarity).

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Question: What was happening in the American music scene when The Beatles performed at the Hollywood Bowl in 1964?

Martin Lewis: The audience was still in the 1950s. They were still in that gray Eisenhower decade, but The Beatles were in 3D Technicolor … just giddy and optimistic and exuberant with their own energy, their enjoyment of music. And America was sorely in need of that authenticity and that expression of youthful vitality.

When they took the stage at the Hollywood Bowl, the fan reaction was incredible. You couldn't actually hear the music because the fans were screaming so loudly. Of course, later The Beatles became louder than the screams.

What role did The Beatles’ manager, Brian Epstein, play in that show selling out in four hours and just the overall rapid success of The Beatles?

On Christmas Day 1963, practically nobody in America had heard of The Beatles. And yet, by the time of “The Ed Sullivan Show” 45 days later, 73 million people tuned in. How did that happen? It was triggered mainly by Brian Epstein having secured a contract for them to appear on “The Ed Sullivan Show” at a time they didn't even have a record contract in America.

He went about convincing Capitol Records to sign The Beatles, and he did that by saying, “Hey, I've got them on ‘Ed Sullivan.’ ” The record was released on the day after Christmas, which was crucial because kids were at home. So instead of hearing the record on the radio maybe two or three times a day, they were hearing it 10 times a day.

By the time of “The Ed Sullivan Show” on Feb. 9, 1964, they were already No. 1. It took what was already exploding and just took it into the stratosphere.

If you think of the wonderful enthusiasm for Taylor Swift – a terrific artist – it was like that times 100 million. It is no disrespect to Taylor Swift and her incredible fans, but the electricity of The Beatles and their success without the internet was astonishing.

That hysteria faded decades ago, but The Beatles' music still endures. Do you think the latter would surprise the Fab Four of 1964?

It would have surprised The Beatles to know that their music would last that long. But if we take a broader perspective, it shouldn't surprise us.

We don't say 'Oh, that Shakespeare, he's 400 years old, we don't want any of his plays.' Or we don't say about the Marx Brothers, 'Oh, it's so 1930s, it's not funny.' It's just either good or it's not good. And what The Beatles did was timeless because it connected with the noblest part of the human spirit, which is the part that yearns to make itself and the world a better place.

The laws of celebrity physics are: You come along, you're successful for a few years, you fade away. Each new generation discovers The Beatles and says, “Wow, this stuff's fantastic.”

The songwriting team of John Lennon and Paul McCartney led to an evolution of the rock ‘n’ roll sound. What did each of them bring to The Beatles’ distinct sound?

What most artists did was they got better at doing the same thing. You played guitar better, you sang better. Your lyrics were a little more interesting. The Beatles weren't interested just in getting a little better. They were interested in changing the boundaries of what you could do. Their approach to songwriting, the topics, the lyrics, the sophistication of all the elements was just unimaginable beforehand.

There was no way that as great as they were, Chuck Berry, Elvis Presley, Buddy Holly could never create what The Beatles created. They could only work with the building blocks they had.

What is Beatles must-see TV today? What will you be listening to or watching to commemorate this 60th anniversary moment?

The one song that says it all is the song that they recorded and performed live to the world in 1967 called “All You Need Is Love.” Four hundred million people live on the world's first-ever satellite linkup.

It's a message to all of us to look to our better angels. They're passing the torch to us, and we, in turn, pass it on to the next generation. That's the message for the ages. All you need is love. Of course, we need a bit more than that. But love is a start.