EXAMPLE FOR ANALYSIS, No. 1.
Bach: Two-voice Invention No. VIII., in F-Major.
The subject or theme of this invention is a melody of two measures' length, first given out by the soprano, and consists of two motives or characteristic figures, one in eighth-notes, staccato, making a series of leaps, thus:
![[PNG]](#5102994518728001825_pag34_score1.png.id-2288060764469464784.wrap-0.html.html){kind=link}
and one a graceful descending run in sixteenth-notes, thus
![[PNG]](#5102994518728001825_pag34_score2.png.id-6521430388206084234.wrap-0.html.html){kind=link}
Notice how charmingly the staccato and the legato are contrasted in these motives.
The entire invention is made out of this subject by means of those methods of varied repetition discussed in Chapter I., especially "imitation" and "transposition." For example, the lower voice, which we will call the bass, "imitates," almost exactly, through the first eleven measures, what the soprano says a measure before it. On the other hand, in measure 12 the bass starts the ball a-rolling by giving the subject (this time in the key of C), and the soprano takes its turn at imitating. Then, from measure 29 to the end, it is again the soprano which leads and the bass which imitates. The student should trace out these imitations in detail, admiring the skill with which they are made always harmonious.
There are many instances of transposition also, most of them carried out so systematically that they form what musicians call "sequences."
A sequence is a series of transpositions of a motive, shifting it in pitch either upward or downward, and carried out systematically through several repetitions. Examples: measures 4, 5, and 6, transposition of the motive in soprano, three repetitions; measures 21, 22, 23, transposition of motives of both voices, three repetitions; measures 24, 25, transposition of motives of both voices, two repetitions. The second of these sequences is shown in Figure X.
It will be noted what a strong sense of regular, orderly progress these sequences impart to the melodies.
It is interesting to see that the same general scheme of keys is embodied in this invention that we have observed in folk-songs: i. e., the modulation to the "dominant" in the middle (measure 12), and the return at the end to the original key. This divides the piece into two unequal halves, the first making an excursion away from the home key, the second returning home—much as the King of France, with twenty thousand men, marched up the hill and then marched down again. Such a two-part structure is observable in thousands of short pieces, and is called by musicians "binary form."
![[PNG]](#5102994518728001825_pag36_score1.png.id-171081295948813352.wrap-0.html.html){kind=link}
FIGURE X. "Sequence" from Bach's Invention in F-Major.
The difference in texture between this piece and any folk-song or dance will best be appreciated by playing over the bass part alone, when it will be seen that, far from being mere "filling" or accompaniment, it is a delightful melody in itself, almost as interesting as its more prominent companion. Indeed, in the whole invention there are only two tones (the C and the A in the final chord) which are not melodically necessary. Such is the splendid economy and clearness of Bach's musical thinking.
Before going further, the reader should examine for himself several typical inventions, as, for example, No. I, in C-major; No. II, in C-minor; No. X, in G-major, and No. XIII, in A-minor, in this set by Bach, noting in each case: (1) the individuality of the motives used, (2) the imitations from voice to voice, (3) the sequences, (4) the modulations, (5) the polyphonic character, as evidenced by the self-sufficiency and melodic interest of the bass, and (6) the structural division of the entire invention into more or less distinct sections.