"Accessible" can be a dirty word in contemporary classical music. For decades, composers have outfitted their works with gnarly tangles of complexity, and heaven forbid if there's a tune you can hum.

In a study by two researchers at University College London, 10- and 11-year-olds were asked to write an “exciting” story. Some wrote while listening to exciting music—"I Spy, The Looking Glass" (a ...