Philadelphia’s Flux Capacitor is a jam band that manages to sidestep any of the easy pigeonholes endemic to the breed. While so many of their brethren indulge in a brand of loose, long-form wankery that harkens back to the Grateful Dead, or at least to one of the Dead’s many stylistic godchildren, Flux Capacitor favor an approach that recalls the high-wire technical derring-do and structural savvy of ’70s prog and art-rock, shades of Yes and early King Crimson.

And yet even the band’s proto-prog inclinations have been recast with strong ’90s alt-rock radio sensibilities, making for memorable songs that manage to be tuneful, toe-tapping and malleably jam-worthy all at the same time.

Flux frontman Peter Sprecht is at a loss to pin down the elusive nature of Flux Capacitor’s sound. Is it pop-rock? Is it prog? Or is it something else entirely? He’s suspicious, however, that it all has something to do with the band’s familial synergy. The band’s lineup includes Peter on guitar and vox, along with siblings Jason Sprecht on drums and Michael Sprecht on keys.

“We’re not entirely sure what makes us be us,” says Sprecht. “But I think it might have something to do with the chemistry the three of us have. Our separate personalities pull it in different weird directions, yet it’s still tight at the same time. There’s some sort of telekinesis there. It’s hard to define it, but there’s something special at the heart of it.”

By Peter’s telling, music was an inexorable calling, the peal of which all three Sprecht siblings heard at an early age. “When I was a kid, I was already singing along to every song I heard on the radio,” he says. “As we got older, we all three wanted musical instruments for Christmas; we all had a really natural drive to play music. I wrote my first song in sixth grade, and in eighth grade, Jason and I played our first show together.”

Sprecht says he and Jason headed up a couple of bands over the years, but nothing with serious sea legs. Then in 2009, they brought in youngest brother Michael for the first time to collaborate in the recording of a single —  “Everything’s Happening” — that turned into a full-length album — “They Know We Know” — that turned into a full-time band. “We all loved the song so much,” Peter says. “It was so much better than anything we had done before. With the three of us there, it was like we had finally found that perfect combination.”

Flux Capacitor is a frequent flier now on the jam-band and festival circuit. The band logs in excess of 130 shows a year, and took the stage at Bonnaroo Music and Arts Festival in 2016. They’ve recorded three full-length studio releases — including the aforementioned “They Know We Know,” the follow-up “Monolith,” and 2013’s “Cycle 9.” But the trio’s latest is a live album, “Live Spirals,” from the 2016 Bonnaroo performance, a record that perhaps best captures the bewildering essence of the band’s brotherly voodoo.

“That particular night was pretty insane,” Peter Sprecht says. “It was an amazing, adventure-filled set, and a really exciting show.”

Flux Capacitor will play Preservation Pub Sunday, Oct. 15 at 9 p.m.