If you’ve heard “BTSTU,” “Jasmine,” or the leaked demos we once thought constituted his debut album, you’ve fallen under the spell of Indian R&B futurist Jai Paul. But did you know you might have listened to and loved music by his brother, too? A.K. Paul was involved in the creation of Jai’s music as well as tracks such as Jessie Ware’s “Imagine It Was Us,” Sam Smith’s “Nirvana,” Big Boi’s “Higher Res.” And now he’s released a solo track of his own, a collaboration with the London singer Nao. It’s bold, humongous retro-futuristic R&B with chipmunk vocals, a guitar solo, a gospel choir, and synthesizers that sound like pogo sticks. And as the title attests, it’s “So Good.” Check it out.