This chapter discusses French Baroque organ music from published and manuscript sources, its liturgical context as well as the instrument itself. Throughout the period, the French organ retained a consistency of design and liturgical use that was unique. Its overriding principle was that of tonal color, so that titles of individual pieces, plein jeu, fugue, duo, récit, trio, and grand jeu, became established genres from 1665 to the Revolution. These genres implied appropriate styles of composition. Nevertheless, within strict parameters, composers were more and more influenced by contemporary Italian and French secular music. This mix of sacred and secular styles was a catalyst for composers of immense imagination: Nivers, Lebègue, Raison, François Couperin, Boyvin, De Grigny, Marchand, Dandrieu, to Michel Corrette and Balbastre, whose music serves as an example of how true creativity developed within relatively narrow parameters.