A form of instrumental music existed in the German Protestant Church which was peculiar to that institution, and which was exceedingly significant as forming a connecting link between organ solo playing and the congregational worship. We have seen that the choral, at the very establishment of the new order by Luther, became a characteristic feature of the office of devotion, entering into the very framework of the liturgy by virtue of the official appointment of particular hymns (Hauptlieder) on certain days. As soon as the art of organ playing set out upon its independent career early in the seventeenth century, the organists began to take up the choral melodies as subjects for extempore performance. These tunes were especially adapted to this purpose by reason of their stately movement and breadth of style, which gave opportunity for the display of that mastery of florid harmonization in which the essence of the organist’s art consisted. The organist never played the printed compositions of others, or even his own, for voluntaries. He would no more think of doing so than a clergyman would preach another man’s sermon, or even read one of his own from manuscript. To this day German unwritten law is rigorous on both these matters. The organist’s method was always to improvise in the strict style upon themes invented by himself or borrowed from other sources. Nothing was more natural than that he should use the choral tunes as his quarry, not only on account of their technical suitableness, but still more from the interest that would be aroused in the congregation, and the unity that would be established between the office of the organist and that of the people. The chorals that were appointed for the day would commonly furnish the player with his raw material, and the song of the people would appear again soaring above their heads, adorned by effective tonal combinations. This method could also be employed to a more moderate extent in accompanying the congregation as they sang the hymn in unison; interludes between the stanzas and even flourishes at the ends of the lines would give scope to the organist to exhibit his knowledge and fancy. The long-winded interlude at last became an abuse, and was reduced or suppressed; but the free organ prelude on the entire choral melody grew in favor, and before Bach’s day ability in this line was the chief test of a player’s competence. In Bach’s early days choral preludes by famous masters had found their way into print in large numbers, and were the objects of his assiduous study. His own productions in this class surpassed all his models, and as a free improviser on choral themes he excelled all his contemporaries. “I had supposed,” said the famous Reinken, who at the age of ninety-seven heard Bach extemporize on “An Wasserflüssen Babylon” at Hamburg,—“I had supposed that this art was dead, but I see that it still lives in you.” In this species of playing,