As frontman for the jam-band Phish, Trey Anastasio shares strengths as an improviser, shredder and tonal colorist that outweigh more modest abilities as a singer/songwriter. But the guitarist managed to tap all those skills (well, apart from the shredding) in a rare solo acoustic concert at Sanders Theatre on Saturday, while chatting up fervent fans with casual stories than exposed him as a sincere, down-to-earth guy.

“How many of you actually go to Harvard?” the New Jersey native piped to only a few hands in the campus hall, telling those who snagged the toughest local Phish-related ticket in some time, “You’re not so smart. You’re just regular, like me.”

His sister Kristy, who died of cancer in 2009, did attend Harvard, and Anastasio’s mid-set tribute “Miss You” and the likewise lyric-hinged “The Line” (inspired by a basketball player who missed critical foul shots in a college championship) were better served in the solo setting than in tempering full-band Phish shows. But the guitarist also spent time roaming with fingers and feet, utilizing his pedal board to trigger loops, washes and tonal change-ups that gave him space to solo over Phish standards “Wolfman’s Brother,” “Free,” “Maze” (its multi-tiered gallop turned to jaunty, clipped low notes) “Twist” and a delicately funky “Tube.” And he kept the night’s focus on Phish tunes, honoring requests in the islands-flavored fable “The Lizards” (laughing when fans picked up the melody after he scatted off-key, noting the song had “so many chords”) and the classically tinged “My Friend, My Friend.”

Anastasio’s rambling tales ran from playful to somber. He spoke of being hooked on rock by hanging with a fellow eighth-grader’s older brothers in the late ’70s, revving a motorcycle on blocks, sampling beer and “dirt weed” and listening to Mountain’s “Mississippi Queen.” He revealed how in Phish’s early days, he caught obsessive roommate/drummer Jon Fishman trying a wheatgrass enema. And in the most touching moment, the guitarist choked up during an account of sitting bedside to boyhood friend Chris Cottrell, who was dying of cancer, serenading him with a softly finger-picked instrumental, shared on Saturday as “’Til We Meet Again.”

Breaking the reserved setting of the acoustically resonant Sanders Theatre, Anastasio inspired a few hearty sing-alongs, balancing the two-hour show with punchier favorites “Sample in a Jar,” the new “Blaze On,” “Chalkdust Torture” and a final “Wilson,” where fans chimed in call-and-response as loudly as they would in arenas. They had reason to be eager. Phish hasn’t played New England since 2016 and that likely won’t change in 2018 (unless there’s a rare fall tour or year-end visit), given no scheduled dates on an upcoming summer tour. A heavily rumored August festival return to Watkins Glen, N.Y., still looms. Even so, while those marathon blowouts provide a peak die-hard experience every few years, they’re the polar opposite of Saturday’s intimate encounter.