J Mascis performs at Slim’s in San Francisco on Nov. 14, 2018. Photos: Joaquin Cabello.

SAN FRANCISCO — A thick blanket of smoke welcomed J Mascis to the Bay Area when he played Slim’s on Wednesday night, and that seemed appropriate.

Mascis, former frontman and guitarist for the famously loud ’90s grunge band Dinosaur Jr., took a minimalist approach for this tour in support of his new album, Elastic Days. He stood on stage with only an acoustic guitar and a Vox amplifier for company, creating an impression that this wasn’t a concert, but a campfire, with the audience sitting around it, and the smell of smoke hanging in the air.

J Mascis performs at Slim’s in San Francisco on Nov. 14, 2018.

Mascis launched into the gentle acoustic strumming of “Thumb,” from his 1996 album, Martin + Me, and “Listen to Me,” from 2011’s Seven Shades of Why.

“I’ve got a new album out and here are a couple of songs,” Mascis told the audience after pausing to tune his guitar.

He then launched into “I Went Dust,” which began as another slow acoustic ballad. But about halfway through the song, after Mascis manipulated some effects pedals, he was suddenly playing a searing guitar solo over a loop he had just created. Hearing that roaring fuzz sound emerge from the same nondescript acoustic guitar he had just been gently strumming caused some wonderful cognitive dissonance. The wall of carefully constructed fuzz tones crashed over fans and Mascis transformed from an unassuming folk singer into guitar god.

J Mascis performs at Slim’s in San Francisco on Nov. 14, 2018.

J Mascis’ legendary guitar tone, still instantly recognizable from the old Dinosaur Jr. albums, will no doubt have guitar nerds debating the minutia of his rig in the Internet forums for days. The guitar pyrotechnics likely reminded fans why Mascis was No. 86 on Rolling Stones’ 2015 list of 100 greatest guitar players.

Mascis kept up this sonic duality, punctuating beautiful and sad acoustic renditions of songs from throughout his career with blistering guitar solos, on “Ammaring” from the 2000’s J Mascis and the Fog album More Light, and on the title track from his new album.

Mascis’ instantly recognizable voice and lyrics still contain all sorts of contradictions. He sounds as if he believes the problems in his songs to be both profoundly meaningful and utterly meaningless; he’s both old and bitter, and young and naive.

The solo acoustic arrangements allowed Mascis to stretch out and add gentle filigrees and flourishes to his song’s simple chord progressions, and Mascis conjured all types of gooey, spacey, clean guitar tones as well on songs like “Web So Dense” and new cut “See You at the Movies” before breaking back into shredding guitar solos.

Mascis also played a number of classic Dinosaur Jr. songs, including “Get Me,” from 1993’s Where You Been?, “The Wagon,” from 1991’s Green Mind, and an eight-minute epic shred-heavy version of “Alone,” from 1997’s Hand it Over as the set’s closer.

James Elkington performs at Slim’s in San Francisco on Nov. 14, 2018.

For an encore J Mascis performed the classic Dinosaur Jr. song “Blowing It” along with his noisily romantic rendition of The Cure’s “Just Like Heaven.” The crowd sang along. Mascis waved casually to the audience and walked off stage, once again transformed into an unassuming mortal.

The show began with British-born, Chicago-based James Elkington turning in a solo acoustic set of gentle Leo-Kottke-sounding folk music. Elkington wooed the crowd with songs from his 2017 album, Wintres Woma, including “The Hermit Census.”