Jacob Kasher's string of hooky hits began in 2009 with Cobra Starship's winking Leighton Meester collab “Good Girls Go Bad.” Since then he's amassed a list of credits that includes Selena Gomez's cavernous “Sober,” Carly Rae Jepsen's giddy “I Really Like You,” and LunchMoney Lewis' pulsing “Bills”—hits that show how his ear-candy choruses can easily adapt to brooding electro, vibrant pop, urgent hip-hop, and other subgenres of big-tent pop.