There seemed nothing remarkable about the Italian passenger who stepped off the packet boat Columbia as it docked in Philadelphia on June 4, 1805, except that he was tall and, for a man in his mid-50s, prematurely toothless. During the two-month crossing from London, the Columbia's captain had not even bothered to learn his name, addressing him as "Signor Italiano." The man spoke adequate English and had courtly manners, but he was broke and had to beg a loan from a fellow passenger to pay the duty on his few possessions: a violin, some violin strings, a carpet, a tea urn and a trunkful of books.

Although his identity meant nothing on the docks that morning, the stranger was no ordinary immigrant. His story, had he told it to customs officials, would have struck them as fantastic—beyond belief.

He was Lorenzo Da Ponte, the librettist who, with Mozart, had created three of the greatest operas ever written: The Marriage of Figaro, Don Giovanni and Così fan Tutte. He was a priest, a poet, a freethinker and a friend of Casanova's. He had flourished in the royal courts and glittering societies of Europe, conducted notorious love affairs and collaborated with some of the leading writers and musicians of the age. He had also, at times, endured catastrophic flops, suffered betrayal and defeat in backstage intrigues, been hounded by scandal and fallen into bankruptcy.

And now, having left London one step ahead of a constable who sought to arrest him for bad debts, he had arrived in America to do what he had already been obliged to do several times in his tumultuous career: start over.

During the 33 years that Da Ponte would spend in the aptly named New World, he would need to put forth vast exertions of persistence, resilience and deft improvisation in order to make his way. Fortunately, as recounted in Rodney Bolt's lively new biography, The Librettist of Venice, he had displayed these qualities in abundance from the beginning. He was born Emanuele Conegliano, the son of a Jewish leather worker in a small town in the Venetian Republic. When he was a teenager, his father converted to Catholicism, and in accordance with custom Emanuele was baptized in the name of the local bishop, Lorenzo Da Ponte.

He went on to seminary, where he mastered Latin, Greek and Hebrew and showed a flair for writing verse. He was ordained and taught briefly in church schools. But Venice, fashionable, dissolute and nearby, exerted an irresistible lure for a dashing young abbé with Da Ponte's wit, charm and ambition. Soon he was mixing with the city's aristocracy, gambling, writing poetry and moving from one mistress to another. (One tried to quiet the neighbors' whispers about "the priest's whore" by claiming to be his sister.)

By 1779, when Da Ponte was 30, Venetian authorities were investigating his louche reputation and history of scandal. He had already been convicted of sedition for publishing some fiery poetry excoriating local political corruption. It was all too much for the republic's ruling council, which banished him. For the first of many times in his life, although surrounded by real enough rivals and enemies, he had proved the most effective agent of his own destruction. (He later conceded that he was "like the soldier who, spurred on by the longing for glory, rushes against the mouth of the cannon.") Also for the first of many times, he fled, penniless, across a border, to the Austrian Empire.

After false starts in Dresden and elsewhere, he settled in Vienna and maneuvered his way into an appointment as official poet to the Italian opera company under the patronage of Emperor Joseph II, a post he held from 1783 to 1791. These were his glory years. He was in demand to write librettos for Salieri, Paisiello and other eminent composers of the day.

What we most want to hear about, however—the magical collaboration with Mozart—is curiously undocumented. Virtually neighbors, the two men had no need to write to each other, so all we get in Bolt's biography is passing mentions in Mozart's letters and unilluminating descriptions in Da Ponte's less-than-reliable memoirs: "As soon as I wrote the words, Mozart set them to music."

What we do know is that by this time, the early 1780s, Da Ponte was a skillful dramatic craftsman, and Mozart was, well, Mozart. Together, they took the erstwhile knockabout conventions of opera buffa and invested them with a new seriousness. They created characters of rare depth and psychological richness, and infused comic plots with a worldly, humane and compassionate view of human frailty.

Meanwhile, Da Ponte's frailties took what was becoming their accustomed toll. He had more affairs and fathered an illegitimate child (his third, after two in Venice). He lost his footing in a shifting political landscape, and his career began to have more downs than ups. When he was finally sacked from the opera house, he went to Trieste, where the new emperor, Leopold II, was traveling, to plead for reinstatement. He lost his case but found a wife.

She was Nancy Grahl, whose German-Jewish father and French mother had lived for years in England and embraced Anglicanism. Spirited, attractive and like Da Ponte an accomplished linguist, she was 20 years younger than the 43-year-old reprobate. The wedding ceremony, if there was one, was probably Jewish, an ironic closing of the circle for Da Ponte, who had long abandoned his priestly garb and vocation. Nancy would be his staunch, patient wife for 40 years and bear him six children.

They spent the first decade or so of their marriage in London. Again, Da Ponte wangled a job as poet to the local Italian opera company. But in contrast to Vienna, he had few opportunities to write new librettos, being relegated largely to the tasks of cutting, patching and revising works for revivals.

He remained, as always, a prolific versifier, translator and polemical writer, but his literary work was not lucrative. In London, he branched out to become a seller of Italian books and a publisher of librettos. Nancy opened a stylish coffee room in the opera house. She prospered; he didn't. When financial storm clouds gathered, she went on ahead to America, where several of her relations had settled. As soon as Da Ponte arrived in Philadelphia almost a year later, and presumably after borrowing more money for the fare, he hurried to New York City to join her.

Da Ponte immediately had to face up to a fundamental difference between his new home and England or Austria: the raw, young United States had no opera world for him to latch onto. "I well knew that my dramatic talents would avail me but little in this country," he wrote. And he quickly proved, once more, that his other talents did not include running a business. Using Nancy's savings, he made two disastrous ventures, first as a grocer in New York and Elizabethtown, New Jersey, and later as a dealer in medicines and general merchandise in Sunbury, in central Pennsylvania.

"Imagine how I must have laughed at myself," he wrote, "every time my poet's hand was called to weigh out two ounces of tea, or measure half a yard of 'pigtail' [plug tobacco], now to a cobbler, now to a carter, or pour out, in exchange for three cents, a morning dram." Yes, but it was no laughing matter.

Salvation—and the discovery of a new mission—came from an encounter in a New York bookstore with a cultivated young man who was captivated by Da Ponte's firsthand knowledge of Italian literature. The man, who would prove a loyal friend and benefactor, was Clement Moore, later to achieve a sort of immortality as the author of "The Night Before Christmas." He gave Da Ponte entree to his patrician circle of friends and family.

The old rogue was launched again—as a teacher. Never mind that Italian language and literature were, as Da Ponte put it, "about as well known in this city as Turkish or Chinese." Here was another cannon-mouth for him to rush against. On and off for the rest of his life, he tutored, he established schools and took in boarders, he staged "assemblies" at which his charges spoke only Italian and performed short comedies and operas. He even had some success in another fling at bookselling, numbering among his customers the Library of Congress.

In short, he established himself, in the words of pianist and musicologist Charles Rosen, as "the unofficial ambassador of Italian culture in America."

At the behest of Columbia University's board of trustees, one of whom was Moore, Da Ponte became, at 76, the university's first professor of Italian. The post was largely honorific, and after the first year he attracted no students. Still, it was a milestone in Italian studies in America. Da Ponte also had a hand in establishing New York's first opera theater. Typically, he was outflanked by his fellow entrepreneurs and ended up with no management role; he also went so far into hock that he had to sell his private collection of books. The venture folded after four years, but it laid important groundwork for the Metropolitan Opera, which came along 50 years later.

Italian to the core, rooted in 18th-century Europe, Da Ponte nevertheless was, when he died at 89 in 1838, a proud American citizen. He was buried not in Venice or Vienna but in New York, where he lies today.

Indeed, what is most striking in the whole Da Ponte saga is how American he became. He lived in the United States longer than in any other country, including Italy. Although he had no quarrel, in principle, with royalty or aristocratic societies, he took to America's democratic spirit. "I felt a sympathetic affection for the Americans," he wrote. "I pleased myself with the hope of finding happiness in a country which I thought free."

His character, for better or worse, displayed many of the traits that we like to think of as distinctively American, starting with his boundless optimism and his endless capacity to reinvent himself. His failings—he was vain and gullible, a schemer and a victim of his passions—were never dishonest or mean-spirited. He was not a cynic like Casanova (who once, when Da Ponte was in a financial scrape, wrote to suggest that Nancy should exploit her charms for money). Warmth, generosity, enthusiasm and an indomitable joy in life were his cardinal qualities.

He never forgot that his primary genius was for writing librettos, and his peak achievement his work with Mozart; but he had a lesser genius for teaching, which yielded the greatest achievements of his American years. The countless men and women who were touched by this gift, wrote Clement Moore, would remember their sessions of tutoring with Da Ponte "as among the sweetest moments of their existence."

Significantly, one of the poems that got Da Ponte in trouble back in Venice was an elegy inspired by the revolutionary fervor that swept the American colonies in the 1770s, titled "The American in Europe." It caused a furor. But in the long run it was nothing compared with the impact of the Italian in America.