Dr. Gossett performs an excised number from Verdi’s “La Forza del Destino” in 2010. (Jason Smith/University of Chicago)

Philip Gossett, a musical sleuth who combed European libraries to recover, reassemble and revive forgotten works of the 19th-century masters Rossini and Verdi, a labor that allowed modern-day listeners to experience music unheard for a century or more, died June 13 at his home in Chicago. He was 75.

The cause was progressive supranuclear palsy, said his son David Gossett.

Among the most ardent opera lovers — the kind who adore the standards but also yearn for music beyond the warhorses trotted out in movies and cartoons — Dr. Gossett was revered for his decades-long campaign to rescue abandoned works from the dust if not the dust bin.

He helped reintroduce Gioachino Rossini, the composer known popularly for the fun-filled “Figaro! Figaro! Figaro!” aria from “Il Barbiere di Siviglia,” as a master not only of opera buffa, but also of opera seria. And in celebrated critical editions of musical scores, Dr. Gossett undid the tinkering of censors to present operas as their early audiences never heard them.

Much like the Constitution, classical music sometimes pits originalists — paladins of what they consider the composer’s original intent — against those who regard a musical score as a living document open to interpretation that may change with the ages.

Dr. Gossett, a longtime professor at the University of Chicago, fell somewhere between the two camps. He recognized — and often admonished purists — that operatic scores were never static documents.

During a composer’s lifetime, even from one performance to the next, an opera might undergo changes to accommodate a singer who couldn’t hit a high note, or to humor a diva who could. Dr. Gossett noted that Gaetano Donizetti, in his opera “Lucia di Lammermoor,” substituted a flute for a glass harmonica when the glass harmonica player became mired in a contract disagreement.

At the same time, Dr. Gossett had little patience for interpretations that relied lazily on tradition or a singer’s whims. Writing in his definitive book “Divas and Scholars: Performing Italian Opera” (2006), he eviscerated the many excuses he had heard from singers who ignored a composer’s instruction:

“ ‘The audience expects it.’ ‘My public demands it.’ ‘If I don’t sing it, they’ll think I don’t have it.’ ‘What would my mother say?’ You name the justification, I’ve heard it.”

Essentially, Dr. Gossett aimed, through rigorous scholarship, to help singers, conductors, musicians, directors and opera houses present performances that were historically, musically and artistically coherent.

In one noted example of Dr. Gossett’s precision, his critical edition of the works of Giuseppe Verdi fixed a slight but significant change to the libretto perpetrated by censors. In “Rigoletto,” the tragic tale of a court jester and his efforts to seek revenge on the Duke of Mantua, the duke enters an inn and demands of the innkeeper, “Una stanza e del vino!” (“A room and some wine!”) — or so the scene was long delivered.

Dr. Gossett and his colleagues determined that the original words had been “Tua sorella, e del vino!” (“Your sister, and some wine!”) — a lecherous request that goes a long way to explain the succeeding action in the scene.

“You have to put your hands on it,” Dr. Gossett once told the Chicago Sun-Times of the importance of working with the score. “You have to inhale the ink.”

Dr. Gossett was credited with reviving a tragic version of Rossini’s opera “Tancredi,” usually performed with a happy ending, that the American mezzo-soprano Marilyn Horne performed to acclaim with the Houston Grand Opera in the 1970s.

A perhaps more dramatic achievement was his resurrection of “Il Viaggio a Reims,” an opera Rossini wrote for the coronation of King Charles X of France in 1825 and then cast aside. Over two decades, scouring archives across Europe, Dr. Gossett managed to stitch together the score. The conductor Claudio Abbado led its modern premiere in 1984 in Pesaro, Italy, Rossini’s city of birth.

Some musicians might have felt constrained by Dr. Gossett’s intellectualism. Beverly Sills, the popular American soprano, once remarked of him that “some so-called musicologists are like men who talk constantly of sex and never do anything about it.”

But Dr. Gossett was widely admired among opera singers around the world, who called upon him for his expertise.

In addition to his noted collaborations with Horne, Dr. Gossett coached American soprano Renee Fleming when she delivered the vocal pyrotechnics of Rossini’s “Armida” at the Metropolitan Opera in 2010. For Cecilia Bartoli, an Italian mezzo soprano, he resurrected ornamentation for “La Cenerentola,” Rossini’s take on the Cinderella fairy tale.

“I felt that I was entering a new operatic world,” G.W. Bowersock, a professor emeritus at the Institute for Advanced Study in Princeton, N.J., once wrote in the New Republic of Dr. Gossett’s Rossinian work.

Philip Edward Gossett was born in Brooklyn on Sept. 27, 1941. His father, a furrier, took him to hear Rise Stevens sing “Carmen” at the Met. The opera house’s standing-room section and its Saturday matinee radio broadcasts, along with the piano lessons he began at 5, were his introduction to music.

During high school, he studied at Manhattan’s Juilliard School, to which, it was announced this year, he would donate his collections. After enrolling in Amherst College in Massachusetts, he changed his major to music from physics, receiving a bachelor’s degree in 1963. He received a PhD in musicology from Princeton University in 1970.

Dr. Gossett joined the University of Chicago in 1968 and was a professor emeritus at the time of his death. Among his honors was a $1.5 million award from the Andrew W. Mellon Foundation in 2004.

Survivors include his wife of 53 years, the former Suzanne Solomon, of Chicago; two sons, David Gossett of Washington and Jeffrey Gossett of Piedmont, Calif.; and five granddaughters.

Unlike the strictest traditionalists, Dr. Gossett did not object to updated stagings of operas, such as a production of Donizetti’s “La Fille du Regiment” that removes the action from the Napoleonic Wars and places it in World War I, or a production of “Rigoletto” that moved the story from Mantua to Las Vegas. He asked only that a performance be faithful to a composer’s vision.

“The future of the music that many of us love depends on new audiences,” he once told the Toronto Star. “The audience is graying, and it’s no longer clear to me that among the younger generation there is a sufficiently large group to replace them.”