As Austrian organizers plan celebrations to mark the centenary of the death of “Waltz King” Johann Strauss in June, reports are emerging that when the Nazis co-opted Strauss as a great “German” composer and incorporated his music into the pantheon of Teutonic cultural achievements, they carefully airbrushed out his Jewish ancestry.

According to Otto Brusatti, head of Vienna’s music collection, it had been “generally understood” that Strauss was of Jewish descent, but when Hitler came to power Austria’s pro-Nazi leaders arranged for the removal of a baptism book from the city’s cathedral that documented Strauss’ Jewish roots.

Brusatti also charged that after the war, officials in charge of Vienna’s museums continued to hide the composer’s roots.

Strauss, born in 1825, was a superstar of his time. His “Blue Danube,” “Acceleration Waltz” and “Emperor Waltz” have made him one of the most popular composers who ever lived. He died in June 1899.

Strauss’ third wife, Adele, was Jewish, as was his surviving stepdaughter, Alice Meisner-Strauss.

After the war, she was given back some of the family possessions that had been appropriated by the Germans and by Austria’s pro-Nazi regime. But she was immediately instructed to sell them back cheaply to the city museum.

In particular, the poverty-stricken Meisner-Strauss was ordered to return the jewel of the collection — Strauss’ handwritten score of the comic opera “Die Fledermaus” — as a “gift” to the museum.

Now, with the approaching centennial celebrations, there are growing demands for family heirlooms, estimated by Brusatti to be worth about $30 million, to be handed back to Strauss’ descendants.

According to Strauss scholar and collector Robert Dachs, whose book on the composer will be published in Britain later this year, Strauss’ descendants were grievously wronged, both by the Nazis and by the postwar Austrian authorities.

Strauss’ renown crossed the oceans.

When Strauss visited New York in 1872, he was invited to conduct an orchestra made up of 1,087 musicians and 20,000 singers. It was a task he accomplished with no fewer than 20 assistant conductors.

At the height of his success, Strauss had six orchestras performing in Vienna on any single evening, and he would dash from one concert hall to another to briefly wield the baton.

Just as Hitler used the work of Richard Wagner to provide a collective anthem for the Third Reich, Hitler also appropriated the music of Strauss and Franz Lehar, composer of “The Merry Widow.” They soon became inextricably associated with Nazi Germany’s cultural pageants.

Lehar’s Jewish roots, like those of Strauss, were never acknowledged by Hitler, who reportedly told critics: “I decide who is Jewish.”