"Der Kongreß tanzt" (The Congress Dances) is a pre-World War II German musical film, in which the Russian Tzar meets and falls in love with a common girl when the Congress of Vienna is stuck. It became such a box-office hit in Japan that Studio Ghibli's anime "The Wind Rises (風立ちぬ)" depicted diners in Tokyo in the 1930's singing its theme song "Das gibt's Nur Einmal" all together.
As a student in that era, my father loved the movie for life. Recently, I came across the screenplay in his library and scanned it in PDF. The pages are even-numbered; odd pages are for the Japanese translation. If my understanding is correct, the copyrights for the movie and script book expired in 1981 and 2003, respectively.