Jennifer Decilveo

Lounging in her loose jumpsuit, songwriter-producer Jennifer Decilveo might be laid back in her steel chair laughing in the middle of New York City, but she’s never been more serious. “I’m not a political dick sucker,” she exclaims, her voice echoed by the skyscrapers surrounding a concrete park in Manhattan. “Going to tell you that right now. If I don’t like somebody, they’ll know it.” That hardscrabble, no B.S. attitude might not be for everyone, but the New Jersey native’s authenticity is what has helped some of the biggest names in music churn out hits. Despite her laissez-faire demeanor on one of the hottest days in Midtown in mid-June, one thing is instantly apparent: For Decilveo, songwriting and producing is a serious game. “People who call themselves producers and don’t produce or...