Nunkomm, der Heiden Heiland (Now come, Saviour of the Heathen) appears in three versions. The chorale on which it is based is Martin Luther's adaptation of the original Ambrosian hymn Veni Redemptor gentium. The first of these, for two manuals and pedals, opens with the first measures of the chorale theme in the tenor, imitated at once in the alto register, over a constantly moving pedal bass. The melody is then elaborated in the upper part to form an ornamented line. The second treatment of the chorale is in the form of a Trio, three melodic lines, one for each hand and one for the pedals. Here a contrapuntal imitative opening by the two lower parts is followed by the appearance of the ornamented chorale theme, to which the two lower parts provide a postlude in conclusion. The third version of Nun komm, der Heiden Heiland is described as in organo pleno, il canto fermo nel pedale (for full organ, with the chorale melody in the pedal part). An introductory contrapuntal passage derived from the chorale leads to the solemn appearance of the chorale itself in the lowest register, successive pedal entries preceded by similar prefatory passages. The canonic variations on Vom Himmel hoch (From Heaven on high) were apparently written in 1747 and offered by Bach when he was admitted to the polymath Lorenz Christoph Mizler von Kolof's Correspondierenden Societ�t der Musicalischen Wissenschaften (Corresponding Society of the Musical Sciences). Bach was the fourteenth of a membership limited to twenty scholars and musicians, including, among those now better remembered, Telemann and Handel. The Christmas chorale by Martin Luther first appears in the pedal part of a Canon at the Octave that involves the two upper parts in such canonic imitation. The cantus firmus is again heard in the pedals, in the second Canon at the Fifth, followed by the chorale melody itself in canon at the sixth and in inversion in the lower voice, accompanied by a moving pedal part. Once the chorale has been heard in this form, Bachadds a canon at the third, with the upper part entering first with an inversion of the melody. A canon at the second follows, between the pedal bass and tenor in inversion, and then, at the ninth, between a pedal inversion and the top voice. This varied treatment of the cantus firmus itself leads to a Canon at the Seventh between the pedals and tenor. A Canon in Augmentation sets an augmented tenor part in canon with a more rapid upper part, with the steadier chorale melody introduced by the pedals. The Canonic Variations constitute a remarkable technical and musical tour de force.