By Scott McLennan

At Agganis Arena, the guitarist led a genre-spanning set from tight harmonies to deep-space jams.

(l to r) Billy Strings and Billy Failing at Boston’s at the Agganis Arena. Photo: Sam McLennan

Midway through the second set of his blazing show Tuesday at the Agganis Arena, Billy Strings paused to enthuse over what a great time he had at Fenway Park the day before, watching the Red Sox win their 14th game in a row. Coming from most any other artist, the aside would have felt like pandering to the Boston audience.

Coming from Strings, however, his tale reverberated with the sort of genuine joy you’d hear in the voice of a 12-year-old just back from his first visit to Fenway. Strings went on, “I love bluegrass because it’s an American art form. Kind of like baseball.”

And with that, Strings led the sold-out house in a buoyant singalong of “Take Me Out to the Ball Game” before launching into the tortured, booze-fueled lament “The Fire on My Tongue.”

The setup and juxtaposition of songs perfectly illustrated both the genuineness and range of guitarist and singer Strings, along with his stellar band of mandolin player Jarrod Walker, bass player Royal Masat, banjo player Billy Failing, and fiddle player Alex Hargreaves.

The band sold out two nights at the Agganis Arena as part of a summer swing through the Northeast. Strings used a cane when taking the stage shortly after 8 p.m., the only lingering sign of his recovery from breaking his leg in April while skateboarding backstage at a show.

Strings has a new album coming out Aug. 28, but the show Tuesday focused on well-known selections—both originals and cover songs—in this band’s hefty repertoire. Other than treating the crowd to a debut version of The Kentuckians’ “Out on the Ocean,” and the second-ever reading of the unrecorded original “Half a Heart,” Strings stuck to familiar fare,  but he performed it all with incredible flair. The concert was remarkable for the way Strings and Co. balanced traditional bluegrass, contemporary acoustic fare, and giant-sized improvisation vehicles of the sort that have made this progressive bluegrass unit such a favorite among jam-band fans.

In the first set, a sprawling version of The Bad Livers’ freak-folk gem “Lumpy, Beanpole, and Dirt” and John Hartford’s frenetic “All Fall Down” inspired extensive solos and jams, with Strings moving his guitar playing around from electrified psychedelia to dazzling, unvarnished acoustic picking. Those songs did not overwhelm the band’s traditional songs or its more compact contemporary originals. Failing and Hargreaves, in particular, were given lots of time in the spotlight during the first set, starting with their work on the opening “Leaning on a Traveling Song” and a red-hot version of the traditional “Sally Goodin.”

(l to r) Royal Masat, Billy Strings, and Billy Failing at the Agganis Arena. Photo: Sam McLennan

Strings rounded out the first set with a few of his album staples, including “Living Like an Animal” and a nice pairing of “Must Be Seven” and “While I’m Waiting Here” that highlighted just how in sync these band members are. Strings closed out set one with a high-lonesome gem, “Sophronie,” which featured mandolin player Walker.

After a short intermission, the band began its second set with the politically pointed critique “Wargasm” that had Strings unfurling a long, muscular solo.

From there, the band made a 180-degree turn into the spidery and spectral “Dreadful Wind and Rain.”

“West Dakota Rose” served as a showcase for Walker’s work, with the rest of the band taking turns to play off his lively mandolin leads.

A highlight of the second set arrived when a crew member brought out a vintage can microphone, around which the band members gathered for some tight-knit harmonizing and picking on “Freedom,” “I Only Exist,” and “Richard Petty.”

Strings then took a seat to navigate the jazz and blues influences woven into “Walk on Boy.”

Strings returned to his feet—along with everyone else in the arena—for an epic rendition of “Meet Me at the Creek,” the third of the big three jam pieces. The subtlety and finesse of the bluegrass picking were set aside for raucous and exploratory playing that held together — even as the band launched into deep space.

Strings pushed “Creek” to its limits, likely consuming any time for an encore—but the extended excursion was far more exhilarating than trimming it for the sake of a showbiz trope. Doing what feels right remains central to Strings’ approach, and his fervent following meets that commitment in kind.

Scott McLennan covered music for the Worcester Telegram & Gazette from 1993 to 2008. He then contributed music reviews and features to The Boston Globe, Providence Journal, Portland Press Herald, and WGBH, as well as to The Arts Fuse. He also operated the NE Metal blog to provide in-depth coverage of the region’s heavy metal scene.