“Swan Lake” may be the most famous of all ballets, though much about the original version that had its premiere at the Bolshoi Theater in Moscow in 1877 has long been shrouded in mystery. But recently discovered materials, presented Tuesday at a conference in Moscow, shed new light on its creation and Tchaikovsky’s sometimes rocky beginnings as a ballet composer.

Most modern productions of “Swan Lake” are derived from the 1895 staging at the Mariinsky Theater in St. Petersburg choreographed by Marius Petipa and Lev Ivanov, which had its premiere after Tchaikovsky’s death and for which Tchaikovsky’s score was drastically reordered and rearranged by Riccardo Drigo. The original 1877 Bolshoi “Swan Lake” — with underwhelming choreography by Julius Reisinger — has been more of a cipher to posterity.

Now a cache of materials uncovered during the recent renovation of the Bolshoi Theater by Sergey Konaev, the principal researcher at the Institute for Art Studies in Moscow, helps answer some lingering questions about that first “Swan Lake,” including about its much-altered score, the authorship of its libretto, its casting, and even its costumes.

Mr. Konaev said in an email that he had grown interested in the Moscow “Swan Lake” in 2002 while working on a publication for the 125th anniversary of its premiere, and that he had been “amused that so few materials are known to researchers though it’s one of the key events for Moscow ballet in the 19th century.” So he began searching for documents.

Among the materials he found, he said, were a violin rehearsal score that was believed lost, a viola part with written notes of each orchestra rehearsal, and crucial financial records — including the account books of the theater and its production department. (“Swan Lake” was first mentioned, he said, in 1875 when an advance to Tchaikovsky was recorded.)

The discoveries provide clarity on a number of issues, Simon Morrison, a professor of music at Princeton University who attended the presentation, said in an email. “We now know who authored the scenario, the name of the ballerina for whom the lead role was intended, the specifics of the original costumes and designs,” he wrote. “These issues were hitherto the subject of learned speculation by fine scholars, but without the key source in hand.”

An analysis of the records established that the libretto was written by Vladimir Begichev, a Bolshoi official who was long believed to have had a hand in it, according to Mr. Konaev. He also said that the materials proved that the lead was originally supposed to have been danced by Lydia Geiten, who took part in rehearsals but then withdrew — apparently because she objected to Tchaikovsky’s score. (He noted that the new materials corroborated her statement, decades later, that she had refused to dance in Tchaikovsky’s first ballet because she had found it “boring.”) And the materials shed light on the Bolshoi’s 1880 revision, with choreography by Joseph Hansen.

The newly discovered materials are sure to interest scholars, balletomanes and Tchaikovsky fans as they try to make sense of “Swan Lake,” a seminal but elusive ballet that still changes significantly from company to company; to this day some productions have happy endings, others more tragic ones; with death, often followed by apotheosis. It has long been known that the original ended tragically, with a great flood; Mr. Konaev wrote that the materials showed that Tchaikovsky took a special interest in the production details of the final tempest.