Brooklyn fixture Solange Knowles, Beyoncé’s little sister, is moving to New Orleans. The singer played a de facto farewell gig Monday night at a laundromat on Atlantic and Third avenues, not far from her Carroll Gardens apartment. “She made a final appearance in her home borough for fans and residents before making the move with her 8-year-old son, Julez,” said a spy. “[She] loves the simplicity, warmth and, most importantly, [the] space she can get in the Big Easy.” We’re also told her “studio sessions at home [in Brooklyn] would result in the police being called for noise,” and that she’ll have a recording studio built at her new place in the Big Easy. Tribeca residents Beyoncé and Jay Z also became regular visitors to Solange’s hood at spots like Lucali and Buttermilk Channel. Knowles’ pop-up show at the Boerum Hill laundry joint was part of Vitaminwater and the Fader’s Uncapped Music Series, which has previously hosted surprise gigs by Frank Ocean, Bon Iver, Kendrick Lamar and Santigold. Solange somewhat cryptically canceled a European tour last week — which turned out to be because of her move south with her son. “I am completely devastated,” she posted on her Web site, “but between moving part-time to a new city, starting my son in a new school and writing/recording my new record . . . I had to make the best decision for my health and provide some stability for my family.”