“Dress Casual” is a frequently used title for Mandy Patinkin’s solo concerts, but “Dress for Adventure” might be more accurate. The Broadway and TV star’s show at Strathmore on Thursday night was full of surprises, and Patinkin, in sneakers and with his sleeves pushed up, often sang in a semi-crouch with one foot forward. He looked like he was ready to sprint straight into the audience.

The remarkably pliant-voiced Patinkin also sounded like he could sing forever — and he joked that he might have to, if he kept forgetting lyrics. “I’ll stay here all friggin’ night,” Patinkin declared as he rebooted yet another tune. Flubs didn’t faze him: The whole show was more like a peek at a rehearsal than a polished recital.

So Patinkin sang Stephen Sondheim’s “Children and Art” leaning easily against the upright piano played by Patinkin’s splendid longtime accompanist and music director, Paul Ford. As the generous hundred-minute show (repeated Friday) progressed, Patinkin gripped a towel and mopped his brow like a boxer as he sang. He sang with a coffee mug in hand. It couldn’t have been more laid-back.

You can do that when you trust your talent. Patinkin — Che Guevara in the U.S. premiere of “Evita,” the original Georges Seurat in “Sunday in the Park With George,” Inigo Montoya in “The Princess Bride” — still has as much range, control and dynamism as any man singing theater songs these days. He tiptoed with infectious lilt and accuracy through the not-so-easy 1940s ditty “On the Atchison, Topeka and the Santa Fe,” and if he begins such Rodgers and Hammerstein anthems as “If I Loved You” or “Soliloquy,” as he did Thursday, you can rest easy knowing the finishes will be sure and strong.

The wide dynamic range may be the defining thing about Patinkin. He holds high, bright, delicate notes like they’re baby hummingbirds, then revs into a fortissimo overdrive that has the most dramatic pickup in the business. The changes can be abrupt, even hard-sell; he’s big on sudden effects. He’s a huge personality coming at the crowd with tremendous zest and command. In another era, he’d have been a vaudeville legend.

As it was, Patinkin turned into a spoken-word artist for a patch Thursday, rendering some of the double-talking patter from “The Music Man” into a searing, shouted takedown of Bernard Madoff. How do you follow that? With “Rich and Happy” (naturally) anchoring a Sondheim medley that included “Our Time” and “Broadway Baby.”

Patinkin’s 24-year-old-son, Gideon, joined his father onstage for a touching duet of Harry Chapin’s “Cat’s in the Cradle,” and he charmed the crowd as he lingered for several numbers (more “Music Man,” more Sondheim) with his dad.

“It don’t get no better than that,” Patinkin beamed as Gideon exited to enthusiastic applause.

Pressley is a freelance writer.