"Always leave 'em wanting more."

The entertainment maxim of 18th-century circus icon P.T. Barnum still applies in the 21th century's digital environment as country songwriters are increasingly focused on enticing music listeners to hit the Repeat button, alternately labeled Replay on some platforms.

The concept of playing a song over and over is, of course, nothing new — dashing home from the store to slap a single on the turntable and listen multiple times was one of the joys of the physical record-buying experience in another era. But the artists and writers in that time didn't receive credit when a fan wore out their song. In the data-driven age of streaming, every play gets counted, so an enthusiastic response can generate meaningful business, hyper-illustrated by the success of Pinkfong's "Baby Shark" after kids racked up nearly 8.5 billion plays on YouTube alone, thanks in part to the Replay button.

For most songs, even substantial repeat business doesn't result in a direct financial increase in revenue because the platform pays out in micropennies.

"A fraction of a fraction of a fraction," songwriter Jimmy Robbins ("The Bones," "Half of My Hometown") laments.

But streaming performance has a heavy influence on which songs get worked to AM/FM stations as singles, and a hit in that platform can potentially lead to six-figure payouts.

"You want to rack up those plays so that radio teams and all those different decision-makers pick your song," says songwriter Ben Johnson ("Give Heaven Some Hell," "One of Them Girls") of the Broken Bow act Track45.

To that end, country writers are increasingly looking at subtle tricks that might entice a listener to hit Replay when a song reaches its conclusion. The best way to do that is to make the track feel inconclusive or unresolved — i.e., leave 'em wanting more.

"There's something subconscious about the human brain that when something is unfinished, you kind of want to listen to it again," songwriter Jordan Reynolds ("10,000 Hours," "Tequila") observes. "I don't know what it is about our brain, but it definitely works."

Dan + Shay member Dan Smyers is a key force in the movement. He frequently mentions songs' "replay value" when he breaks them down, and many of his associates — including co-writers Reynolds and Laura Veltz ("Speechless," "I Could Use a Love Song") and video director Patrick Tracy ("10,000 Hours," "I Should Probably Go to Bed") — apply the same concepts to their work.

"I just wrote a song where we only have two choruses," songwriter Laura Veltz ("Speechless," "I Could Use a Love Song") notes. "The motive there was that chorus is a real highlight of the song, and if they hear it three times, are they less likely to want to play it again? Or are they more likely if they only hear it twice? We veer off into this cool bridge thing that sort of makes you think about the chorus, but it's not the chorus. And we did that on purpose, just to see if it leaves people wanting more."

Smyers and his co-writers made a similar move with "I Should Probably Go to Bed," though, he says, it was unintentional. In the duo's current single, however, he very purposely used a pitch-shift technique to turn a Shay Mooney ad-lib into a short, melodic embellishment that sounds like a Mariah Carey-in-the-stratosphere phrase. It occurs only twice, working as a sort of tease.

"It was just another little layer," says Smyers. "When you think you've heard it all, here's one little piece of ear candy that doesn't happen again for about another 45-50 seconds. ‘What was that?' You know, you got to keep listening or you got to go back and listen again. We always like to throw little Easter eggs in like that."

The entire music industry is, of course, built on the Replay concept. Popular radio stations operate under a system that aims to play the songs listeners want to hear most at just the right level of repetition. Earworms — the hooky riffs and melodies that play over and over in a listener's head — are a form of currency that songwriters have tried to generate for decades. Singer-songwriter HARDY says composer Chris Tompkins ("Before He Cheats," "Drunk on a Plane") believed that every hit single contained some addictive element that made the listener want to hear it more than once. The digital age has simply heightened writers' awareness of replay value and the techniques that can improve it.

"Maybe this TikTok era has brought that to life because these TikTok songs are only like 10 seconds, and they play that magic part, which is the part that you want to discover," says HARDY. "A lot of people are becoming conscious of that, and they should be. I think that's what makes a hit."

The desire for "Repeat" customers has led songwriters on some occasion to bring their songs to an abrupt, incomplete halt at the end, says songwriter Hunter Phelps ("I Don't Know About You," "Drinkin' Beer. Talkin' God. Amen"). And it has inspired some to write their songs shorter, thinking listeners may be led to extend their engagement.

"Whenever ‘Old Town Road' came out, it wasn't a very long song," says Phelps. "I definitely listened to that like three times in a row right when it first came out, and it might have something to do with how short it was and how smashy the melody was."

One other trick is to withhold melodic resolution, best understood perhaps through the Rodgers & Hammerstein song "Do-Re-Mi" from The Sound of Music. Near its climax, Julie Andrews sings "ti" — the seventh note in the scale — for an extended amount of time. Viewers sometimes lean forward in their seats at that moment, itching for the song's resolution on "do." But what if the writer never brings us back to "do"?

"I have always been a big fan of ending on [a] chord that doesn't say the song is done," says Robbins. "I do think people are subconsciously affected when they don't feel like it's over, and they might be more likely to start it again."

That becomes even more significant if the song's lyric fails to be resolved. In the 1960s, Stax songwriter David Porter ("Soul Man," "Hold On, I'm Comin' ") noticed that most Motown recordings left their storylines open-ended, and he became a successful writer by employing that same approach. Underscoring the point, uncertainty is a key component in classics from that period, such as Bobbie Gentry's "Ode To Billie Joe" and Otis Redding's "(Sittin' On) The Dock of the Bay," but it's also intrinsic in current titles such as Chris Stapleton's "Starting Over" and Miranda Lambert's "Settling Down."

"At a philosophical level, when you're writing a song about life, most stuff in our life is not resolved," says Robbins. "It's hard to put a period on things just because it's not very realistic."

Ultimately, while it's beneficial to have songs with high replay value, the devices that create that may not be realistic for many copyrights. So while the techniques are being batted around more frequently in Nashville writing rooms, they also get batted down a bunch, too.

"I don't want it to affect the art too much," says Robbins. "Because it is such a special thing. When I take a step back and I'm like, ‘Whoa, we just made something up that didn't exist five hours ago,' that's actually kind of amazing. I feel like if I really peeked behind the curtain too far, I might never come back."

This article first appeared in the weekly Billboard Country Update newsletter. Click here to subscribe for free.