Photo by Zoran Orlic

Could Trampled By Turtles –speedgrass’ beloved sons for more than a decade – be slowing down? If the acoustic quintet’s seventh studio album, Wild Animals, is any indication, this string-happy bunch is yielding to an invisible construction worker on the side of the road holding a big orange sign. Produced by fellow Minnesotan Alan Sparhawk of Low (a trio known more for its restrictions than embellishments), the release takes its time in beautiful ways, and the live show follows suit.

Kicking off a three-month fall tour at Chicago’s Riviera Theater on Sept. 4 with a string quartet and extra cellist thrown in for good measure, the band delivered its new roster of songs with languid elegance. “Repetition” found frontman Dave Simonett utterly vulnerable without a Mumford-ized catharsis to use as a crutch while Dave Carroll birthed a new genre on the title track that this review is coining banjo trance.

Unfortunately, a venue devoid of functional air conditioning marred this sonic detour. It’s hard to fault the Turtles for a temperature crisis; and on a crisp, harvest moon-filled night, most would welcome the tradeoff of velocity for emotional heft, but stuck in the middle of a sauna, the crowd craved fast and dirty. Sensing the mood of the “hot, thick room,” as Simonett characterized it, and surely suffering the same nauseating stickiness, the group set the strumming into high gear at evenly paced intervals. “Western World” rumbled as if the Turtles guzzled a mixture of Pop Rocks and Pixy Stix backstage and Erik Barry’s mandolin busted the barn doors wide open on “Help You” (one of the night’s many selections from 2010’s career-boosting Palomino ).

For close to two hours, the Turtles exercised workmanlike precision with no patience for idle chitchat. Ryan Young’s astonishing prowess on the fiddle expressed more than any canned banter could communicate. Doubled over as if suffering from acute appendicitis, Young weaved his bow until the slow-burning waltz “Bloodshot Eyes” creaked and moaned like a Tall Ship dancing on the waves. His histrionics on “It’s A War” catapulted this Appalachian cousin into the psychedelic stratosphere inhabited only by Willy Wonka’s creepy boat ride. 2005’s “Codeine” donned a Tennessee strut by way of the Great Lakes.

What the band lacked in improvisational gusto, it made up for in ingenuity. A cover of the Pixies’ “Where Is My Mind” came as no surprise to devotees, but still sparked a joyful welp from those undeterred by the suffocating heat, just as a campfire-ready rendition of The Band’s “The Night They Drove Old Dixie Down” closed it all out with a silly grin.