About an hour after the War and Treaty burned down April’s Stagecoach Festival in California with a scorching rendition of “The Star-Spangled Banner,” the married country duo are cooling down in an air-conditioned trailer as they ponder a question: Who sang the greatest national anthem of all time?

“To me, it has to be Whitney Houston,” Tanya Trotter says, to which Michael Trotter Jr. nods in agreement. “There’s a Mount Rushmore, though,” he adds. “No. 2, Chris Stapleton. No. 3 — this is debatable — I think Jennifer Hudson.” He runs a comb through his hair as he considers a fourth. “Kelly Clarkson does a really good job. Beyoncé does a great job.”

No room for Marvin Gaye, who performed a famously sultry interpretation at 1983’s NBA All-Star Game? Michael crinkles up his face.

“Oh, that’s the worst version,” he says.

“We should not go on the record saying that,” Tanya advises.

Michael: “I’m not afraid. I’ll go on the record.”

Tanya: “Here we go.”

“I want to think of the service and of war and how me and my battle buddies fought for freedom,” says Michael, who began writing songs as an Army soldier stationed in Baghdad during the Iraq war. “So, Marvin Gaye — I just don’t like it.” He grins. “But that’s OK. If Tanya wants to do it to his version, hell, yeah — let’s do it. Now, it’s the best version ever.”

Two decades after Michael’s experience in Iraq, the War and Treaty has carved out a space as one of the most exciting live acts in American roots music, with a catalog of wise and passionate songs about loyalty, faith and romance, and a boisterous stage show that evokes memories of Ike and Tina Turner. In February, the Nashville, Tennessee-based couple — Michael is 42, Tanya, 50 — were nominated for best new artist at the 66th Grammy Awards (despite having released their fourth studio album, “Lover’s Game,” in 2023).

Zach Bryan recruited the Trotters to appear on his smash self-titled LP from last year, then asked the duo to open for him in early June. In July, they share the bill with the Rolling Stones.

“It’s absolute magic, the two of their voices together,” says country star Nate Smith, whose new EP, “Through the Smoke,” features a harmony- drenched collaboration with the War and Treaty. Smith remembers seeing the duo perform “That’s How Love Is Made” at November’s Country Music Association Awards and being brought to tears by the intensity of the emotion in their singing. “We’re talking beyond goosebumps,” he adds. “I was literally bawling — like, ‘What is wrong with me right now?’ ”

Indeed, the Trotters have become reliable showstoppers at Nashville’s many televised awards events, including the Academy of Country Music Honors (where they paid tribute to Stapleton last year with a sexy-churchy take on his song “Cold”) and CMT’s recent “Smashing Glass” special (where they got Patti LaBelle fanning herself as they belted LaBelle and Michael McDonald’s classic “On My Own”).

The format is an ideal showcase for the War and Treaty’s sweaty blend of country, rock, gospel and R&B: To see the Trotters lock eyes and voices is to believe them. But according to the couple, it’s also the only available remedy to a vexing problem.

“People talk all the time: ‘They’re just awards-show babies,’ ” Michael says. “Yep, you’re right — we are. Because the reality of the situation is that we’re not getting played on country radio. So we’ve got to treat TV like you would radio and try to get on every awards show we can. And when we get on there, we’re gonna try and do the same thing every single time, which is to blow the roof off until people understand that we’re here to stay.”

Even in an era defined by streaming, country radio retains much of the genre’s hitmaking power. And though the War and Treaty are part of a growing number of Black voices in Nashville — think also of Kane Brown and Mickey Guyton and Brittney Spencer — playlists remain thoroughly dominated by white men, including those visiting from other styles: Compare the immediate No. 1 showing by Post Malone’s “I Had Some Help” on Billboard’s Country Airplay chart to Beyoncé’s peak at No. 33 with “Texas Hold ’Em” from the much-discussed “Cowboy Carter” album that she has said was inspired by the country industry’s cold shoulder. (One of Beyoncé’s collaborators, Shaboozey, may have an exception on his hands with “A Bar Song (Tipsy),” which is steadily rising at country radio.)

Asked if they feel welcome at a festival like Stagecoach — other acts on this year’s bill included Morgan Wallen, Hardy, Jelly Roll and Miranda Lambert — Tanya says “Definitely,” while Michael reflects for a moment. “I don’t think it’s enough to feel welcome,” he says. “There’s something else to feel, which is to feel together. And when you have artists standing onstage yelling about redneck culture, you know they’re not talking to you. So I think what we have to do as a culture is we have to stop laying out the welcome mat and really start extending the hand. There’s a difference.”

As a committed purveyor of songs about love — not about the pain of its absence but about its promise of spiritual fulfillment — Michael acknowledges that the War and Treaty is out of step with most modern country music, which he says is “based on heartbreak.” He laughs. “It’s the truth: Morgan’s main song is ‘Last Night’ ” — Wallen’s chart-topper about a couple’s drunken breakup — “and then Hardy’s out here singing about ‘I woke up on the wrong side of the truck bed.’ I look at that and I’m like, ‘Is this where War and Treaty fits? Is this where we show that there’s still a market for art that focuses on love?’ ”

The Trotters, who’ve been married since 2011 and have a 13-year-old son, sing and write with the familiarity of longtime partners.

In “The Best That I Have,” a simmering slow jam from “Lover’s Game,” Tanya joins a lover on the couch with ice cream and reruns of “The Golden Girls.” And onstage, the two communicate with an unspoken intimacy, signaling each other with just a look or a touch on the wrist to take a vocal line or to hold back.

“Me and Tanya, we share time and space in every way,” Michael says.

The couple have plans to release an album early next year, although they’re booked solid on the road for the rest of 2024, including festival dates and opening for the likes of Bryan, Lyle Lovett and Gary Clark Jr.