Polytonality is the combination of more than two key signatures played simultaneously. Bitonality is the use of two simultaneous keys. While initially polytonality referred simply to contrapuntally juxtaposed tonalities, it quickly was applied to any simultaneous tonalities that cross, overlap, complement, or even oppose each other. An example would be Stravinsky’s ballet Petrushka, where the first clarinet plays a melody in the key of C major while the second clarinet plays nearly the same melody in the key of F# major. Polytonality is considered to be a technique of 20th-century music, however, earlier examples can be found in Wolfgang Amadeus Mozart’s Ein musikalischer Spass (1787), where he used the technique for comic effect. Charles Ives, who was a businessman by day (Ives & Myrick insurance in New York), and a composer by night, was an early pioneer of polytonal music, although Darius Milhaud, (French composer of works that combine jazz, polytonality, and Brazilian music) used it perhaps more than any other composer.