As a kid, Molly Lewis was obsessed with learning to whistle. “I just really needed to make a sound with my mouth,” she says, at ease on a sofa at home in LA one Tuesday morning. “It was a fun thing for me, and I was good at it.” So good at it, in fact, that it’s become her full-time gig. Since 2016, Lewis has worked with musicians as diverse as Mark Ronson, Dr. Dre and Kirin J Callinan, and released two EPs of her own. “I still pinch myself,” she says.

Elle Hunt: What makes a good whistler?

Molly Lewis: People often ask me for whistle lessons, but I don’t really know how to teach it. It’s just about trying to form your mouth in many different ways. It’s not one size fits all—you need to play around. I definitely have a talent for it, but I honed the skill over many...