The great song explosion of 2020: Why Paul McCartney and other artists are dropping albums at a pace we haven’t since the 1960s.

One of the biggest magical mysteries of the 1960s for me — as someone who experienced the era not in the moment, but as history — is how much music the marquee acts of the decade made, and the rate at which they made it.

In 1965, for instance, the Beatles released not only the underrated Help!, but also the masterpiece Rubber Soul. That same year, Bob Dylan blew minds by going electric twice with Bringing It All Back Home and Highway 61 Revisited.

Not to be outdone, the Rolling Stones put out three LPs in ’65. Creedence Clearwater Revival matched that number in 1969, and let loose with two more in 1970.

How’d they do that?

In the modern era, technology has made it much easier to make music and reach fans directly. Your laptop is your home studio, the internet a distribution network. Yet artists rarely release music with anything close to the frequency of those brash baby boomers when pop was coming of age.

Major stars now go years between projects. In the last eight years — more than the entire length of the Beatles' recording career — Rihanna has released only one album, 2016′s Anti, without diminishing her star power one bit.

But in 2020, changes are afoot. The coronavirus pandemic has turned the music industry inside out. Acts like Paul McCartney, Taylor Swift, Jeff Tweedy, and Drive-By Truckers are all putting out music that they never planned to make. And, suddenly, unleashing multiple albums in one calendar year doesn’t seem so outlandish.

Back in January, the Truckers issued a state-of-the-union opus called The Unraveling. This month, the band followed it up with The New OK, a surprise sequel whose new songs address the roots of far-right political demagoguery (“Sarah’s Flame”) and this summer’s season of civil unrest (“Watching the Orange Clouds”). For kicks, it also includes a winning cover of the Ramones' “The KKK Took My Baby Away.”

For the Juneteenth holiday, the British soul and funk band Sault — a mysterious aggregation as skilled at keeping their identities secret as they are at making music that speaks with power and grace to the Black Lives Matter moment — released an album-of-the year candidate called Untitled (Black Is).

That was impressive enough, considering that Sault had also issued two albums in 2019. More stunning still is that the group then came back two months later with Untitled (Rise), another tour de force, created in response to the death of George Floyd and global protest moment it inspired.

» READ MORE: Who is Sault? The mystery collective’s new album doesn’t say. But it speaks to the BLM moment with power and real grace. | Review

This past week, Adrianne Lenker, front woman of the band Big Thief, put out two gorgeously delicate albums on the same day, one with words, called songs, and another without them, instrumentals. Both were recorded in isolation in April in a one-room cabin after Big Thief’s touring plans were nixed.

Rapper Ty Dolla $ign also released a star-studded new album, Featuring Ty Dolla $ign, and has another one already in the can, which he told New York magazine he’d probably release later in the year. “When you make seven songs a day, you get a new playlist,” he said.

Also released this past week: Love Is The King, the new solo album by Wilco leader Tweedy, who has been performing The Tweedy Show on Instagram Live nearly nightly from his home in Chicago since the pandemic began. His sons Sammy and Spencer often join him.

On Love Is The King he employs his offspring on a set of homespun songs that cope with the jagged nerves and unavoidable sadness of life under lockdown with tenderness and compassion: “Life isn’t fair,” he sings. “Love is the King.”

And news arrived this week of more music on its way that was recorded under lockdown — though in this cases by a musician who didn’t need the assistance of any family members in his pod to create an album of new songs.

That would be Sir Paul McCartney, who announced that on Dec. 11, he’ll release McCartney III, the third in a series of true solo albums — he plays every instrument — that began 50 years ago with McCartney I. (McCartney II came out in 1980.)

In a statement accompanying the announcement, the ever cheerful Macca talked about how the unplanned album came to be in response to the living conditions he found himself unexpectedly in.

“I was living lockdown life on my farm with my family” — he charmingly uses the word “rockdown” at one point in the news release — “and I would go to the studio every day … I had to do a little bit of work on some film music and that turned into the opening track and then when it was done I thought, what will I do next?”

So, what’s the connection between all this unexpected musical activity in 2020 and the prolific recording output of artists like McCartney and his Beatles bandmates back in the day?

Just this: Those baby boom acts who were coming of age in the 1960s were fecund for a lot of reasons. They were creatively on fire, and were part of a youth culture revolution that was remaking the world at a time of social upheaval.

But they also were making their names at a time when the concert business was still in its infancy.

The touring infrastructure that now puts acts on the road for months and years at a time on each album cycle didn’t mature until the early 1970s. (The Spectrum, the South Philadelphia showplace with an illustrious arena-rock history, didn’t open until the fall of 1967.)

So artists were in the habit of doing quick promotional tours, then going back into the studio to make more music, and hopefully, more money.

In this century, that model has flipped. With downloading and now streaming, earnings from recordings are negligible. The best way to get paid is to head out on the road to sell tickets and merchandise, and stay there.

Thanks to COVID-19, however, that’s not an option in 2020.

So musicians now have ample time to create more music in private — perhaps partly to compensate for the misery of not being able to do their jobs in public — and to send it out into the world. Music fans are starting to see the results of that woodshedding. No shows, but more songs.

Country rebel Sturgill Simpson had to come off the road in March. He was further sidelined by a COVID-19 diagnosis. But he’s just released Cuttin' Grass: Vol. 1, a double album of bluegrass songs that he says will be followed by a second volume before the year’s out.

So far, much of the best music that artists have record under lockdown — Swift’s folklore, Tweedy’s Love, Sault’s Rise — has a deeply personal feel that’s free of distractions and addresses important matters at its own pace.

In other words, it does what McCartney says he wound up doing in McCartney III. “It was about making music for yourself rather than making music that has to do a job. So, I just did stuff that I fancied doing. I had no idea this would end up as an album.”