The two pop music titans, locked in a close contest for the top of next week’s album chart, are stoking fans’ competitive spirit with a variety of digital tactics.

“Hit Me Hard and Soft,” the new album from Billie Eilish, left, is competing with Taylor Swift’s “The Tortured Poets Department” for No. 1 on next week’s Billboard 200 chart.Credit…Marcelo Hernandez/Getty Images; Kevin Mazur/TAS24, via Getty Images

A cold war between pop music titans — or at least their mobilizing fan bases and record labels — turned into a digital arms race this week as both Taylor Swift and Billie Eilish gunned for the No. 1 spot on next week’s Billboard album chart.

Swift, 34, has occupied the top of the Billboard 200 for the past four weeks with her blockbuster new album, “The Tortured Poets Department,” which has earned more than 3.6 million equivalent album sales so far (counting physical purchases, downloads and streams). But Eilish’s well-reviewed new album, “Hit Me Hard and Soft,” is challenging for No. 1 in its debut, as its 10 songs prove popular on streaming services like Spotify.

If only it were that simple.

Already, some impassioned followers of the two artists had been stoking a rivalry, dating back to comments Eilish made in March about “some of the biggest artists in the world” selling many vinyl versions of the same album, “which ups the sales and ups the numbers and gets them more money.”

The tactic, which Eilish called “wasteful” and damaging to the environment, has been widespread but used especially broadly — and effectively — by Swift. (Even before those comments, Eilish’s brother and main collaborator, Finneas, had once been heard on a hot mic joking about being “sued by Taylor Swift” after performing with an artist who had criticized her work.)

Eilish, 22, said later that she had not meant to single out any artist with her vinyl comments and added that she had participated in the practice, too. (Both artists’ work remains available in a variety of physical formats, though Eilish has stressed sustainability.)

Still, when Swift pre-empted the release of Eilish’s album last week with three special digital editions of “Tortured Poets,” available for 24 hours and including previously unheard “first-draft phone memo” demos, many saw the move as pointed. Especially online, where pop fan allegiance can be a blood sport, the matchup became one to watch.

Eilish soon released her own new digital edition of “Hit Me Hard and Soft,” which added isolated vocal tracks for each song. Such maneuvers — in which listeners invested in the chart success of their favorites are incentivized to stream and buy more with bonus content — are popular and common, especially amid close contests for bragging rights, in the chess game that is the modern music business. But it didn’t end there.

On Tuesday, Swift released a remix of her hit “Fortnight”; on Wednesday, Eilish posted a new remix of “L’Amour De Ma Vie.” And on Thursday, the final day of Billboard’s tracking week, Eilish expanded her album again, releasing limited edition versions of each song both slowed down and sped up. (Eilish’s labels, Darkroom/Interscope, also discounted “Hit Me Hard and Soft” to $4.99 as an iTunes download — a more popular chart-minded move in an earlier era of digital sales — while Swift’s “Tortured Poets” remained at $14.99. Swift’s “Fortnight” remix was priced at 69 cents, less than the typical single price of 99 cents or $1.29.)

Then, on Thursday evening, with six hours left in the sales window for the week, Swift made what seemed to be a final push, releasing three additional digital versions for sale on her website, each of which featured a new live track from her Eras Tour performances earlier this month in Paris. The special editions were made available for one day only.

Midweek predictions, which predated some of the latest bonus releases, gave Swift the slight edge, with an estimated 350,000 equivalent units to Eilish’s 300,000, according to Hits magazine, whose totals sometimes vary from the official count. (Eilish’s previous album, “Happier Than Ever,” sold 238,000 in its first week, slightly less than the 313,000 units her debut sold in 2019.)

Billboard said the race “could be a close one.” And even unaffiliated fan groups — Arianators, Katycats, Little Monsters and so on — were being called upon by fans to line up behind one side or the other.

Representatives for Eilish and Swift declined to comment. The final count will be revealed early next week.