A few months after graduation, Bach, armed with a recommendation by the Graun brothers (Johann Gottlieb and Carl Heinrich) and Sylvius Leopold Weiss, obtained an appointment at Berlin in the service of Crown Prince Frederick of Prussia, the future Frederick the Great. Upon Frederick's accession in 1740, Bach became a member of the royal orchestra. He was by this time one of the foremost clavier players in Europe, and his compositions, which date from 1731, include about thirty sonatas and concert pieces for harpsichord and clavichord. During his time there, Berlin was a rich artistic environment, where Bach mixed with many accomplished musicians, including several notable former students of his father, and important literary figures, such as Gotthold Ephraim Lessing, with whom the composer would become close friends.