The mellifluous sound of Viennese music streams throughout the culturally-rich city as musicians proudly perform the works of the city's most famous musician: Wolfgang Amadeus Mozart. One of Mozart's first concerts was at Vienna's Schönbrunn Palace. The child prodigy was extolled by Austrian royalty, particularly by Empress Maria Theresa. After the performance, he leapt into the empress's lap, hugged and kissed her. Throughout his life, Mozart returned to Vienna several more times. When he became an independent musician, he made the city his home, working as a successful musician, performer, teacher and composer. Mozart played and collaborated with Joseph Hayden and other composers and worked with Librettist Lorenzo da Ponte on enduring operas like "The Marriage of Figaro" (1786) and "Don Giovanni" (1787). Although Austrian Emperor Joseph II preferred the Court Musical Director Antonio Saleri after a contest he had commissioned between the two musicians, the emperor hired Mozart as an imperial chamber composer to write dance music for the Vienna Court. Mozart died on December 5, 1791 in his beloved city. The cause of death is still unknown and disputed. He was buried in an unmarked common grave with four or five others in the city's St. Marx cemetery. Although his burial site is unknown, a memorial grave in the cemetery commemorates the timeless musician.