Cassandra Wilson performs the first of two shows at the Howard Theater in Washington. (Josh Sisk/FOR THE WASHINGTON POST)

The word “dark” isn’t often used to describe the human voice, but in Cassandra Wilson’s case it’s more than apt. Low-pitched and smoky, the jazz singer’s instrument has a haunting, mysterious quality that’s amplified by the rootsy but often melancholy arrangements she uses. That sound was belied by her manner at the Howard Theatre on Wednesday, which had the warmth of an old friend. In song, though, that dark-hued folk-jazz sound was intact.

Wilson confined herself to a chair at center stage. “So as you can see I’m seated. I’m gonna work the chair though,” she noted with a grin, reinforcing the comfortable feeling of her presence and the folksiness of the music. Her choice of tunes, including the Beatles’ “Blackbird” and her own “A Little Warm Death,” did the same. To these, Wilson added touches reflective of her artistic persona.

“Blackbird,” while instantly recognizable, assumed a light funk tack, via bassist Lonnie Plaxico and drummer Mino Cinelu, and a beautifully swinging solo by pianist Jon Cowherd. “A Little Warm Death” was characterized by sly interplay between Wilson’s scat and the harmonica of Gregoire Maret.

For all the technical craft in her music, Wilson’s unerring ability to channel soul and feeling truly elevated the performance. There was joy in her “Another Country,” dedicated implicitly to President Obama’s re-election with the simple introduction, “Today we’re in a new country.” Then there was Meshell Ndegeocello’s soft, delicate “Come Bare Your Soul to Me,” which Wilson sang as a whispery jazz ballad with lyrics as open and welcoming as the title. But her penetrating voice, along with Brandon Ross’s ruminative classical guitar solo, turned the song into what was less an invitation than a piece of deep introspection.

Wilson, 56, held court from the stage, encouraging audience members to interact with her. The level of that interaction soon became grating; still, Wilson was endlessly patient, even obliging a particularly obnoxious spectator’s request for the standard “You Don’t Know What Love Is” with a sublimely passionate, head-in-hands rendition that was a brilliant match for the natural darkness of her singing.

“Yeah, I needed to sing that,” she told the persistent fan. “Thank you.”