By Paul Robicheau

The sheepishly affable Trey Anastasio wisely focused on music, allowing him to play a broader representation of his repertoire across two hours and 25 minutes.

Trey Anastasio at the Boch Wang Theatre. Photo: Paul Robicheau

Trey Anastasio’s solo acoustic concerts — like the one that drew a sold-out audience to the Boch Wang Theatre on Sunday — don’t outwardly play to his strengths. As leader of jam-band pioneers Phish, Anastasio hasn’t garnered acclaim as a singer or songwriter as much as for his fluid prowess on electric guitar, particularly within that band’s improvisatory flights.

Sitting on a chair at center stage with just an acoustic guitar and microphone, Anastasio initially played the role of troubadour, offering his flock a chance to hear his songs in stripped-down form. He opened with Phish’s “Theme from the Bottom,” slipping into a very brief jam that hinted at the night’s direction.

A few songs in, he also broke the ice like many a troubadour by telling a story: that Phish played the Wang 31 years ago for the Boston Music Awards, where they rushed through “Rift” and noticed Aerosmith in the front row, thinking to each other that “they’re so old!” Anastasio chuckled that he researched it and that Aerosmith members were 15 years younger than he is now at 60.

A lesser tale about comedian Steven Wright backstage at a 1996 Phish show provided the only other long story. The sheepishly affable Anastasio wisely focused on music, allowing him to play a broader representation of his repertoire across two hours and 25 minutes.

As with Phish, he’s maintained his spontaneity with set lists, serving entirely different songs each night. And he’s been tackling a growing number of that band’s knottier epics in his solo shows, aided by occasional pedalboard effects and — toward the end of the show — a keyboard accompanist.

He nonetheless eased into Sunday’s intermission-free show with more basic fare, both upbeat and subdued. Rootsy rocker “Back on the Train” became a surprise early standout, Anastasio playing a resonant low-string tone against its choppy strum — making one imagine the incubation of Phish songs. The bluesy “46 Days” likewise hit a breezier groove to Anastasio’s amplified foot-tapping before he looped a pulsing chord to free up his fingers for a short solo.

Love songs can be his Achilles’ heel. The ballad “Shade” remained mawkishly sentimental, though the humble, earnest “Waste” struck a lovely chord as a solo rendition away from arena environs that strain his voice. And “Summer of ’89,” a Phish tune that disappeared after 2010 performances, turned into one of Sunday’s highlights. As if intimately picked for a back-porch date, the song hit a sweet spot as a dedication to his wife and the arc of their relationship.

Anastasio flashed his guitar skills on an early “My Friend, My Friend,” a prog-leaning tune whose laced chords and feathery notes transitioned nicely to the acoustic. And after a confident charge through “Chalk Dust Torture,” he hit a peak stretch when pianist Jeff Tanski came out to turn the last five numbers of the main set into a duo performance. After gliding through the harmonic-iced instrumental “Till We Meet Again,” the two delivered a sterling run through the cycling ascension of “Taste,” a slow-blossoming “If I Could,” and a climactic “Reba.” Nursery rhyme-like choruses gave way to its winding composition (Anastasio slapping a few drum breaks on his guitar body) and its blissful jam. Sure, it’s better with Phish as a full band, but this lent an intriguing changeup.

Trey Anastasio at the Boch Wang Theatre. Photo: Paul Robicheau

The duo tackled greater challenges in the encore. In a salute to Aerosmith, Anastasio resurrected the bluegrass-flavored “Rift.” If it wasn’t as rough as Phish’s BMA rendition, the guitarist had some trouble nailing its high-fret tightrope with full-toned notes, though having the piano as a foil paid off. Finally, Anastasio unveiled the real showstopper, a 15-minute “Fluffhead,” a revered if tricky-to-execute suite.

Fans rose to their feet for the Wang “Fluffhead,” chiming the opening lyrics before Anastasio settled into relaxed, well-sung verses, followed by delicate syncopation with Tanski. If not entirely flawless, his intricate guitar lines were a pleasure to hear in stark, sinewy relief. The duo wound in counterpoint, the multipart song culminating in its triumphant if silly title refrain and coda.

After that final stroke, buzzing fans spilled onto the sidewalk, and an evening that began like a folky recital felt more like a Phish show — and not just for the obnoxious hustling of nitrous oxide balloons outside the venue.

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.