If we tend to envision the short life of Wolfgang Amadeus Mozart as primarily unhappy — ever at odds with his wife, impoverished and in debt, driven to an early grave by his rival Antonio Salieri — it is largely because of Peter Shaffer’s play “Amadeus” and Milos Forman’s film adaptation of the same name. But as the historian Paul Johnson writes, that portrayal is very much a fiction, and in his slim new biography, Johnson seeks to counter the most egregious misconceptions.

Was Mozart’s life fundamentally tragic? Not if you consider that he was an “easygoing person, whose brief spasms of hot temper and outbursts of grievances were mere cloudlets racing across a sunny view of life,” Johnson writes. “He enjoyed existence and wanted everyone to be as happy as he.” Deeply religious, Mozart could be exceedingly charming, while also displaying a crass sense of humor. He indulged his passion for dancing and billiards, all the while composing an astonishing number of symphonies, operas, concertos and chamber works. How could such a life be considered tragic? Indeed, Johnson writes, the real tragedy is that Mozart did not live to write more, having died at 35.

True, cash was often short in the Mozart household, and the composer did incur debts and write letters to his friends begging for money. But Johnson notes that debt was common in Mozart’s day, due in part to a currency shortage. Mozart was actually “in the top 5 percent of the population in terms of earnings. He was a member of the select upper-middle class of pre-Revolution Austria. . . . Of the five different apartments he had in [Vienna] at various times, all were commodious. . . . He had a horse for exercise when he chose. He had a valet. He traveled by private coach. He dressed as the Chevalier Amadeus. He had access to a country dwelling beyond the suburbs. There were plenty of parties.”

If Johnson believes “that music historians have bothered too much about Mozart’s income,” he takes greater issue with the demonization of Mozart’s wife, Constanze, sometimes depicted as a slovenly, wasteful figure. Yet the evidence for this interpretation, Johnson writes, “is slight. Where it exists, it tends to be second- or thirdhand, usually dating from the 1820s or 1830s, over a quarter century after Mozart’s death. He never expressed criticism of her household management. . . . The truth, so far as I can judge, is that Constanze was always a good wife and mother, ran the household well, but was out of action a large part of the time, either pregnant or nursing or in Baden in desperate attempts to regain her health and strength.”

Even when Johnson advances a compelling argument, however, he never substantiates it by citing specific sources; time and again, we are simply expected to take him at his word. “It seems to me,” “I think,” “I believe,” “I suspect,” “so far as I can judge” — these phrases pepper far too many of his assertions. Equally arbitrary are his musical judgments. Much of this book reads like an iPod playlist: Johnson tells us what his favorite piano sonatas are, which violin sonatas “show Mozart at his best,” which operas he prefers and so on. What’s missing is anything other than the most superficial sort of musical analysis. In proclaiming the greatness of “The Marriage of Figaro,” Johnson praises the felicities of the opera’s libretto, its general optimism and happy ending — in other words, the story — with barely a word about the sublime music that fills every page of the score.

"Mozart: A Life" by Paul Johnson. (Viking)

Yet far worse is the sloppiness of Johnson’s writing — some banal phrases and verbal tics, but mainly the amount of repetition. We learn, multiple times, that Mozart’s earliest compositions were either written or edited by his father, that the composer saw very little of his music published in his lifetime, that he was attracted to the secrecy of Freemasonry. In one extreme example, Johnson tells us that “there is some evidence [Mozart] actually preferred the violin and, even better, the viola” and later, in the same paragraph, that he “liked violin playing, and playing the viola still more.” Then, just three pages later, Johnson tells us yet again that “Mozart, himself, preferred to play the viola rather than the violin.” All this would detract from a book three times as long, but in a work of just 155 pages of text? (I am not counting a tacked-on, if engaging, appendix by the journalist and historian Daniel Johnson.)

Johnson’s portrait of Mozart, master of melody, form and instrumental sonorities, gives the impression of having been tossed off far too quickly. Thousands of books have been written about Mozart. Johnson’s addition to this hefty mass of scholarship, well-intentioned though it may be, needed — at the least — a careful, attentive editor.

Bose is the managing editor and fiction editor of the American Scholar.