 When Frederick II became King of Prussia in 1740, Quantz finally accepted a position as flute teacher, flute maker and composer at the court in Berlin.He joined that court in December 1741 and stayed there for the rest of his career.He made flutes from at least 1739 and was an innovator in flute design, adding a second key (D#, in addition to the standard Eb) to help with intonation, for example.