By Paul Robicheau

Boston Calling has evolved into a smorgasbord of everything from indie to mainstream, from pop to hip-hop to hard rock.

Chappell Roan at Boston Calling 2024. Photo: Paul Robicheau

Boston Calling pushed its limits in Sunday’s finale when a crowd estimated as high as 40,000 jammed the festival’s adjoining main stages for a combustible parade of popular performers in Chappell Roan, Megan Thee Stallion, Hozier and the Killers. It was a perfect storm, far outpacing the turnout on previous nights for stadium act Ed Sheeran and the fest’s first country headliner, Tyler Childers.

Surging pop supernova Roan, fresh off opening for Olivia Rodrigo, drew a slew of young women who packed the Harvard Athletic Complex by mid-afternoon Sunday, recalling last year’s mob scene for Noah Kahan. They sang along to every word from Roan, who looked like a character from “The Rocky Horror Picture Show” in cabaret whiteface and a red bustier to match her curly locks. Fans related to the relationship paradox of “Casual” and knew the “Y.M.C.A.”-like dance moves that accompanied the bouncy “HOT TO GO!”, creating a sea of in-sync arms. The singer’s backing trio rocked, and her theater-kid emoting drew cheers, but the catchiness of her tunes sealed the deal.

Boston Calling has evolved into a smorgasbord of everything from indie to mainstream, from pop to hip-hop to hard rock — and Sunday offered some rootsy change-ups. The Revivalists followed Roan’s coming-out party with New Orleans-born rock (replete with pedal steel and horns) on the second main stage, highlighted by bare-footed frontman David Shaw’s hop down to the rail in his denim overalls for face-to-face serenades. And, on the soccer field at the other end of the complex, Christone “Kingfish” Ingram served pure modern blues, taking the spotlight with his nimble guitar licks and sustains while also sharing his soulful voice. But once rap star Megan Thee Stallion took reign, the crowd got stuck in gridlock around the main stages.

Megan Thee Stallion at Boston Calling 2024. Photo: Paul Robicheau

Sure, one could argue that Megan Thee Stallion should have headlined. Not only because of her recent chart hits (including feature splits), but because it would have quelled complaints that Boston Calling 2024 lacked a woman or hip-hop act as a headliner. She maintained plenty of poise and charisma along with her rapid-fire braggadocio and precisely controlled twerking (a video camera often fixated on her jiggling butt), starting from her opening callout “Hiss.” Yet a sameness in both sexual jousting and backing tracks suggested that the hour-long slot hit her sweet spot. A few tracks stood out (like “Kitty Kat” with its swing-beat drive), six lithe female dancers complemented her sensual moves, and flame geysers added to the heat. And, for all her lewd innuendo, the rapper acknowledged the crowd with genuine smiles and heart signs. She spotted one fan’s bouquet and summoned it to the stage.

From there, attendees weighed priorities: whether to hold position for the Killers, try to burrow toward the adjoining stage for Hozier, brave a hellish middle ground or settle for the back. Catching Canadian indie-pop faves Alvvays at the far end of the grounds posed a near-impossible task without missing the top-billed acts.

Irish soul-rocker Hozier reinforced his growing mainstream appeal, shifting from moody tribal rock to contemplative, fingerpicked resonator guitar, his performance shaded in darkly dramatic lighting and occasionally textured with cello and violin. Fans sang along to hits “Too Sweet” and “Take Me to Church,” though Hozier set up “Nina Cries Power” with a rambling speech on civil rights and suffrage that proved difficult to distinguish at the outer edges of the wall-to-wall crowd.

After a surprise Saturday show at the Paradise Rock Club, the Killers felt at home on Boston Calling’s largest stage, where they also headlined in 2018. Tight-jacketed singer Brandon Flowers assured fans they were witnessing “purveyors of some of the finest rock ‘n’ roll on Planet Earth” and did his best to match the boast.  He roamed from one stage-front platform to the other with a flourish, belting out hits from “All These Things That I’ve Done” to an encore of “Human” and “Mr. Brightside,” presented as a slow singalong before the arrival of a full rev-up capped by a crowd-teasing drum solo by the dynamic Ronnie Vallucci.

Ronnie Vannucci of the Killers at Boston Calling 2024. Photo: Paul Robicheau

Saturday at the Harvard fields was a much more laidback experience, as close to a country music day as one finds at Boston Calling. Before headliner Tyler Childers, the third stage sported the spirited country-rock of Tanner Usrey, the stylish Red Clay Strays (who open for the Rolling Stones at Gillette Stadium on Thursday), and Jessie Murph, who mixed Alabama twang with her pop and rap. Ward Hayden & the Outliers sealed the country mold on Saturday’s Orange stage, which was kept busy all weekend with local acts (another highlight being Dorchester rapper Kei’s high-energy closing set with dancers on Friday).

Yet Saturday injected its own variety. English rocker Frank Turner & the Sleeping Souls fired up the second main stage with a punk-folk broadside that peaked with a requested mosh pit when he sang “I won’t sit down, and I won’t shut up, and most of all, I won’t grow up!” from his signature tune “Photosynthesis.” Texas trio Khruangbin floated a different mood with exotic, atmospheric funk. Guitar squire Mark Speer dripped glassy chords and trills over the beefy bass of Laura Lee, a dominant force both tonally and visually in her orange dress as they paced steps of a triple-archway-topped platform in casual choreography.

Khruangbin at Boston Calling 2024. Photo: Paul Robicheau

A shift into jam-band terrain was complete when Khruangbin was followed by guitarist Trey Anastasio’s four-piece version of his solo band, which tackled a modest slice of his main outfit Phish’s repertoire. While missing that group’s experimental range, the band hit a slippery flow in jams for “The Moma Dance” and “Everything’s Right,” Anastasio gazing up at the evening clouds — a real-life simulation of what he last saw overhead with Phish at Las Vegas’ Sphere.

Tyler Childers at Boston Calling 2024. Photo: Paul Robicheau

Tyler Childers took advantage of his career-climbing budget to fill the stage with ear and eye candy. His eight-piece band was a crackerjack ensemble with pedal steel, fiddle, dual keyboardists and guitarists, plus acoustic and electric bass. Visuals included a living room TV and lamps and a backdrop that turned from jumping fish, mushrooms, pigs and a camper in space for “Country Squire” to cartoonish church windows. But when he celebrated his wife with an earnest “All You’n” and “Lady May” or pulled out a fiddle hidden in a cupboard for some twin sawing through Hank Williams cover “Old Country Church,” Childers showed that he hasn’t strayed far from his Kentucky roots.

Friday provided a solid warmup in Boston Calling’s appeal to diverse audiences. Renee Rapp filled the Chappell Roan slot in terms of pop demographic and also-rocking band, but she shared a more dressed-down attitude in a long-sleeved T, jeans, and high-tops. The “Mean Girls” star cut back on backing vocal tracks to belt out a heartfelt early hit “In the Kitchen” and departed from her usual setlist to feature “I Hate Boston,” about a “trying time” with exes, inserting a disclaimer to the lyric “They should just burn the whole city down.” In contrast, Leon Bridges should have been warm in his tan corduroy jacket, but his R&B soul could not have been cooler. He eased in, donned an acoustic guitar for “Texas Sun” (albeit without his mates-on-record Khruangbin) and strutted across the stage for the Chuck Berry feel of “Twistin’ & Groovin’”

Ed Sheeran at Boston Calling 2024. Photo: Paul Robicheau

Many musicians have tapped live electronic loops to expand their solo palette onstage, but no one has taken it to stadiums like Ed Sheeran. He stormed out with hard strumming, then thumped the body of his acoustic guitar to add a beat to “Castle on the Hill” before a chorus from the family-dotted crowd lent a layer of its own. And the tousle-haired singer shared his full range by reviving “Take It Back” for the first time in years, launching into animated rapping with detours into cover snippets of “Superstition” and “Ain’t No Sunshine” before going troubadour for the tender Scottish traditional song “The Parting Glass.” Before his last run of hits, including “Shape of You,” he urged fans to sing along, though not to lose their voices for the weekend ahead. They needed little coaxing.

Paul Robicheau served more than 20 years as contributing editor for music at the Improper Bostonian in addition to writing and photography for the Boston Globe, Rolling Stone, and many other publications. He was also the founding arts editor of Boston Metro.