At nearly 21, Kawtar Oudghiri is a long way from the teenager who used to post covers on YouTube after school in Sidi Slimane. A few years later, the singer who first drew attention with her cover of “Ya Lalali” has made a name for herself with a distinctive voice and a restless musical curiosity, moving between R&B, Afrobeats, pop and raï. Now, with “B&N (Black & White),” the first single in a planned trilogy, she is taking that experimentation a step further.