The letter grades that City Paper gives to Spoleto performances aren’t just slapped on haphazardly. On the contrary, factors from crowd reaction to lighting to emotional connection are each assigned a numeric value, before being tallied together to land on a precise, indisputable grade (plus or minus).

Well, we’re throwing all that out the window for Mavis Staples. Forget about the cavernous echoes that muffled the sound. Overlook Staples’ cough and signs of age in her voice. By all means, banish from your memory when she addressed the crowd as “Charlotte.”

Because when Mavis Staples moaned her first husky, guttural breath into the microphone, she had each and every heart in the room.

“We came this evening to bring you some joy, happiness, inspiration, some positive vibrations,” offered Staples. “Enough to last for six months.”

Opening with the a cappella “Wonderful Savior,” a song that could just as easily have served as an encore, she immediately segued into “Creep Along Moses,” also a cut from 2010’s Grammy-winning You Are Not Alone.

The bare bones band, complete with just drums, bass, guitar, and three backup singers (including sister Yvonne), may have actually made controlling the sound more difficult. Although it improved after the first song, the booming drums initially overpowered everything else. (Hint to future bands with drums in the Gaillard: Plexiglass sound wall.)

After the song, Mavis paused for her first extended address to the audience, laughing that they’d met four men named Michael backstage, joking about her bad knees, and commenting that the dressing room was so nice that she might not ever leave town.

“Wrote a Song for Everyone” kept the energy high, before the band broke into a lively version of The Band’s “The Weight.” Staples truly came alive, repeatedly bellowing “put the load on me!” before screaming “Levon Helm! Levon Helm!” to an audience roaring in respectful approval.

As the show progressed, the stripped down band proved their worth, most notably through guitarist Rick Holmstrom’s subtle control of his Telecaster. The group moved into a section of songs derived from the Staple Singers’ early days, including “Freedom Highway” and “Why? (Am I Treated so Bad),” introduced as Dr. Martin Luther King’s favorite song.

Throughout the Civil Rights-era and spiritual numbers, Staples moaned into the mic, stopping between songs to explain that her grandmother once told her that “when you moan, the devil don’t know what you’re talking about.”

After “My Country,” during which Staples called out people who “disrespect the president,” she and Yvonne sat down to let the three-piece band show off while she rested her knees on a chair set just in front of the curtain at the back of the stage.

Staples retook center stage to a roaring rendition of “I Belong To the Band,” singing ‘Hallelujahs’ that inspired the first people to rise from their seats with hands in the air. Waddling around the stage like a Yoda of soul, Staples’ tiny figure belied her commanding presence. Pulling inspiration from the air with hands uplifted high, Staples let out her fateful “Charlotte!” at a pivotal moment in the night’s energy.

What followed was undoubtedly the finest-ever recovery from this familiar faux pas in Charleston.

“That’s his granddaughter’s name. It’s her birthday!” yelled Staples, pointing at drummer Steven “Dr. Good Love” Hodges. “We call her ‘Charlotte Red Dress,’ but I just yelled her name.”

The room having fallen silent, Staples immediately re-acknowledged her present location, opening a monologue about shrimp and grits that led to countless audience members shouting out their restaurant recommendations.

The Charlotte/Charleston flub behind her, Staples lit into her set closing “I’ll Take You There.” Finishing up with the biggest song of a career can be an albatross for many bands, but for Mavis Staples, it’s only natural. Working the audience into a clapping and shouting frenzy until they sang along, the soul legend walked out on a high note, reminding everyone that the Staples family has been taking us there for 62 years. Indeed, they still are.