The second surviving son of Johann Sebastian Bach, Carl Philipp Emanuel Bach studied with his father and musically was the most important and influential of the sons. His career as a whole has been said, by E.F. Schmid, to mark a development "halfway between the world of his father and that of the Viennese classics." After schooling at Leipzig, he took a law degree at Frankfurt an der Oder in 1735. He moved to Berlin in 1738 and became keyboard player for the young crown prince, Frederick of Prussia, who in 1740 became King Frederick II. Bach remained in Frederick's service until 1767 as keyboard performer, composer, and accompanist to other members of the royal musical entourage, which included Frederick himself as flutist and a very distinguished circle of musicians.
Two early sets of keyboard sonatas, the "Prussian" Sonatas (1740) and the "Württemberg" Sonatas (1743), show that by the age of 30 Bach had achieved a fully mature style of composition, less rigorous in its contrapuntal organization than that of his father but with considerable power of invention and formal design and with evident stress on bringing to keyboard composition some of the intense expressivity associated mainly with vocal music; for example, the first of the 1740 Sonatas has an instrumental "recitative" as the slow movement.