Last week at Carnegie Hall, Esperanza Spalding was slashing through a tangle of chord changes on her fretless electric bass. Behind her was a four-piece band; behind it, a symphony orchestra.

She was playing “Good Lava,” a crunchy, hurtling tune from last year’s concept album “Emily’s D+Evolution.” On that LP, her fifth, she moves swiftly and elusively, constantly changing shape and direction.

But recently Ms. Spalding, 32, has grown a little wary of her own ambitions, and for her next album, which she announced on Wednesday, she is heading straight to the creative source. Starting the morning of Sept. 12, she will spend 77 straight hours in the studio, bringing with her a few musicians but no pre-written songs. Over those roughly three days, she will write, arrange and record a full-length album, “Exposure,” while streaming the experience live to a web audience. She is aiming to finish 10 songs, most with lyrics.

“I think of it creatively as a context where you give all that’s been cooking in there permission to come out at will,” she said last week over Mexican food near her home in Brooklyn. “I thought: I just need a break from framing. I’m tired of backing everything up and explaining why this character does this and that.”