Composer, born in Weimar, Germany, the second surviving son of J S Bach. He studied at the Thomasschule, Leipzig, where his father was cantor, and at Frankfurt University. In 1740 he became cembalist to the future Frederick II, and later became Kapellmeister at Hamburg (1767). He was famous for his playing of the organ and clavier, for which his best pieces were composed. He published The True Art of Clavier Playing (1753), the first methodical treatment of the subject, introduced the sonata form, and wrote numerous concertos, keyboard sonatas, church music, and chamber music.