He who chases two hares might catch neither. But he can at least have a great time trying. On October 20, 1874, in Danbury, Connecticut, a child was born who would grow up to be one of the greatest American composers of classical music. More than a half-century ahead of his time, he combined late romanticism, American folk, and avant-garde techniques in a way that revolutionized music.

On the very same day, in the same town, a child was born who would grow up to transform the business of financial planning. An actuary, successful insurance entrepreneur, and well-known financial author, he devised ingenious life-insurance products and created the modern practice of estate planning.

It was not a coincidence that the great composer and the celebrated financial innovator shared a birthday and birthplace. They were the same man: Charles Edward Ives.

You might assume that anyone who worked as both a composer and an insurance executive would see the latter as a necessary evil—a prosaic "day job" to endure so he would be able to write music. Ives truly loved music, and he pursued it with intense passion from earliest childhood. But as the music historian J. Peter Burkholder notes, he also loved insurance. According to his business partner, Julian Myrick, Ives called it a "great mission," adding, "A life insurance policy is one of the definite ways of society for toughening its moral muscles for equalizing its misfortunes." There is no evidence that one career gave him more happiness than the other, nor that he saw either as more inherently creative or important.

Ives's story sounds as if it could never unfold today. With the educational requirements and long hours demanded of most knowledge workers, no one has time to shine at two radically different things. Young people are told to follow the "10,000-hour rule" to excellence; to focus, laserlike, on one thing; and to never multitask in their careers.

To be sure, fixating on a single activity might be a decent formula for maximum output. But the story of Charles Ives—along with a good deal of scientific evidence—shows that hyper-specialization is not the best strategy for our well-being. We can find greater happiness by instead cultivating a variety of serious interests and activities.

Maintaining multiple skills and interests is different from trying to do multiple things at once, or multitasking. Multitasking has been consistently found to lower productivity and work quality. (Contrary to stereotypes, it is just as bad for women as it is for men.) You have probably experienced the frustration of a workday in which you are busier than ever but constantly interrupted and thrown from task to task, and at the end of the day you feel like you haven't accomplished anything.

Not surprisingly, multitasking has negative consequences for happiness. In one 2017 paper, researchers monitoring human subjects found that performing work designed to imitate multitasking made people less calm, less content, and more anxious. Similarly, writing in the Harvard Business Review in 2015, scholars at the University of Pennsylvania and Duke University found that over relatively short periods of time—a few minutes or an hour—changing tasks lowered happiness and made people feel less productive.

But when the UPenn and Duke researchers extended the time people could devote to each task, they found that the happiness effect reversed. As they increased the experiment window from an hour to a full workday, the participants began to derive greater happiness as task variety increased. The researchers' conclusion: "Start by scheduling more varied activities into your days, weeks, and months and removing variety from your hours and minutes."

What happens when we add variety not just to months or years, but to an entire career? In his 2019 book, Range: Why Generalists Triumph in a Specialized World, David Epstein shows that people with varied skills are becoming more valuable in the modern economy, and tend to have the most fulfilling work lives. This has led some academics to question the value of the doctoral degree, and some firms that employ knowledge workers to look specifically for polymaths—or, as the writer Emilie Wapnick calls them, "multipotentialites"—who weave many interests and skills together to form a rich, fun life.

Ives—the quintessential multipotentialite—waxed philosophical about how unrelated things can fit together to enhance a life. "Orderly reason does not always have to be a visible part of all great things," he wrote in his Essays Before a Sonata. "An apparent confusion if lived with long enough may become orderly."

There's an old proverb that goes, "Duos qui sequitur lepores neutrum capit"—"He who follows two hares catches neither." Perhaps that's so, but he who chases two hares can at least have a great time trying, which can be more important in a good life. Many of my graduate students in public policy and business administration have a strong background and interest in subjects unrelated to their academic discipline. My advice to them, based on the truths above, is to not abandon either one.

The interests don't have to be alike. After all, Ives didn't catch two hares—it was more like a dolphin and a rhinoceros. In the 1970s, many social scientists believed that this kind of dichotomy was hard or impossible—that "right brain" creative talent and "left brain" analytic ability generally didn't overlap. But modern brain research shows that activity on the sides of your brain is similar, regardless of your personality. You might have a much greater interest in music than insurance, or vice versa, but your brain is not wired for one or the other, and there is no reason the same person cannot do both well.

That's not to say one person can necessarily make a lot of money chasing two hares. My students often point out that pursuing a dual career might put them on a lower earnings trajectory than throwing themselves single-mindedly into just one thing. Research on the subject is limited, but it's very plausible, and not everyone has the luxury of choosing lower pay. Still, you might be better able to afford a dual career than you imagine: Some economists and investment planners believe that many Americans overestimate how much money they need. Lots of research—and human experience—shows how easily wants become needs, resulting in the relentless pursuit of maximum income, which won't make you happier.

If one of your interests has no earnings potential at all, you can still pursue it with passion. This was the case for Ives, who made little money as a composer and once remarked, lightheartedly, "If [a composer] has a nice wife and some nice children, how can he let the children starve on his dissonances?" In this case, you can pursue an avocation in a serious way—in other words, work hard and play hard. Research has found that a high level of commitment to a hobby makes leisure time significantly more satisfying.

Your interest can also take the form of serious study, whether or not formal classes are involved. My father, a mathematics professor, was every bit as absorbed in his avocational interest in fossils and human origins as he was in his professional career. New hominid discoveries were as likely to be dinnertime conversation as Fermat's Last Theorem. He never made a dime off his Neanderthal pals, but they lit him up like nothing else, and he knew as much as many paleoanthropologists. He was as likely to abandon the hobby as he was to quit his job.

In addition to being fun and making you happy, a commitment to multiple skills can make you better at each of them. Ives certainly thought so. He is often credited with saying, "You cannot set art off in a corner and hope for it to have vitality, reality, and substance. There can be nothing exclusive about substantial art. It comes directly out of the heart of the experience of life."

Perhaps that's why motifs of duality are so prominent in Ives's compositions. He made extensive use of bitonality, juxtaposing pieces of music on top of one another to create unique sonic experiences. In "Three Places in New England," for example, he breaks the orchestra into two groups, each of which imitates a different marching band playing a different song. The conductor is required to direct different meters with each hand, and the result is a strange, joyful cacophony of sound.

You, like Ives, can conduct your life in two meters at once, creating playful clashes, cheerful dissonances, and unanticipated harmonies. You might not be the next great composer of music, but armed with Ives's formula, you can compose a fulfilling life.

Arthur C. Brooks is a contributing writer at The Atlantic, the William Henry Bloomberg professor of the practice of public leadership at the Harvard Kennedy School, a professor of management practice at the Harvard Business School, and host of the podcast The Art of Happiness With Arthur Brooks.