[PNG] [[audio/mpeg]]

FIGURE XVIII. MOTIVES OF BACH PRELUDE IN G-MINOR

Note the effective contrast between the bold, assertive character of motive (a) and the more graceful character of (b).

Structure: The prelude divides itself into seven clearly marked sections, each ended by a well-marked cadence. Let us examine these briefly in turn.

Section I, measures 1-32, key of G-minor: Founded on motive (a), with many sequences which the reader should now be able to trace for himself.

Section II, measures 33-66: Begins in G-minor, modulates to B-flat major, the "relative major." Motive (b) in soprano, measures 33-34; in alto, measures 35-36; in bass, measures 43-44. Motive (a), measures 35, 36, 37 (alto), 38, 39, 43, 44, 53, 54, etc.

Section III, measures 67-98, key of B-flat: An almost exact copy of Section I, in a different key.

Section IV, measures 99-124: Begins in B-flat major, modulates to D-minor, the "dominant" of the original key. Both motives tossed about from voice to voice. (The reader should locate each instance for himself.)

Section V, measures 125-160: Begins in D-minor, modulates to E-flat major, thus giving variety of key in the middle part of the composition, which we begin to see is an important principle of form. (Compare the Gavotte of the last chapter.) Very similar in treatment to Section II.

Section VI, measures 161-179: Modulates back from E-flat major to the home key, thus preparing the way for the final statements and conclusion. In measures 175-178 the insistence of the bass on the tone D, the "dominant" of the original key, will be noticed. Such an insistence on one tone is called a "pedal point," because so frequently found in the pedal part of organ music, and serves admirably here to prepare the mind for the triumphant return to G-minor in the final section. The rest of Section VI is made up of sequences, thus: 162-165, 166-169, 170-173; and then, 173, 174, 175, 176, 177, 178.