(con't from Part XXXI)
As we're traveling the highway noticing the scenery a first glance might cause us to miss something really worthy of our attention.
In a situation like this our aesthetic sense seems to tell us that what we've just noticed really deserves another look.
It's like a little alarm bell goes off inside us to warn us to spend a little more time with it so we don't miss out -- as if a warning sign were posted on the road (photo) for our own good that we should make a "U" turn and go back to fully experience and appreciate what we've just been exposed to.
A glance at our own catalog of compositions might offer us a suggestion in this respect: we might go back and have another look at a Fugue we've already written, turn it's subject around (invert it), and see if it makes another good line.
A good fugue subject (or countersubject) can be expected to sound good when turned upside-down also [See blog, Inversions].
We might then take that inverted subject and create an entirely new Fugue with it, perhaps by enlarging it slightly by including an excursion into an unrelated key in addition to all 5 related keys; then, after that new Fugue is written, we might use one of its countersubjects to build a related Prelude to be paired with it.
Building a second Fugue by inverting another Fugue's subject brings to mind some of what J.S. Bach illustrated when he penned his monumental work to which his sons, after his death, attached the title "The Art Of Fugue."
It's a fascinating trick if the opportunity lends itself and one that will lead us to make many interesting and rewarding discoveries in composition if we just have the courage and will to give it a try.
When the Prelude is supplied with just one theme, it can be worked easily enough, once again, in the 6-part improvisational form that Louis Vierne taught his students to use for improvisation on a single free theme [See blog, Learning By Example, Getting Started With Writing, Part XXXI].
This was the scheme employed in the score of the b minor Op. 26 Prelude & Fugue [See menu bar, Free Stuff]; it's Fugue subject is the preceding Op. 25 Fugue subject in inverted form.
It will help to download and print a copy of this score as this narrative is followed:
The Prelude begins with a 2 bar introduction, adding voice by voice until a 4 voice texture is reached in the 3rd bar which presents the theme in the top line; this theme is 7 bars long, harmonized in 4 parts, and ends in a perfect cadence in the home key of b minor.
The 2nd section, or bridge (Fr. "pont"), connects this 1st exposition of the theme with the 2nd exposition; this bridge need not be longer than 6 bars and generally works well when made up of 2 equal phrases each 3 bars long, the last of which points to the key of the 2nd exposition.
The 2nd exposition is supposed to be in a different key than the home key; the key selected is often the dominant but it could be the relative or some other related key; other less closely related keys might also be used for this if a smooth modulation to them can be made; the Op. 5 and Op. 25 Preludes are examples of this [See menu bar, Free Stuff].
Here the theme reenters in the dominant key, this time in the alto line, and is harmonized again in 4 parts, ending in a perfect cadence in the dominant key.
The 4th or development section takes a bar or two from the theme and works it rhythmically and harmonically for about 20 bars or so before coming to a stop; in this section bits of thematic material undergo excursions through a series of distant keys (A Major, C Major, Eb Major, Db Major, E Major) and arrive finally at a held Ab Major chord.
A length of 20 bars for the development section is merely an arbitrary choice, a compression or shortening of what Vierne generally recommended; extremely shortened, truncated developments sound like they're over with before they've started, whereas very long, tedious developments run the risk of dwarfing the other sections of this form to where the sense of architecture of the piece tends to get lost; a middle ground of around 20 bars, which represents roughly 1/3 of the Prelude, seems to be a reasonable compromise.
How this development section makes its various twists and turns is facilitated by employing sequences [See blog, Sequencing] and is only limited by the composer's imagination; no matter how far afield the music travels away from the home key, a smooth return to the home key can be created in the preparation for the reentry which follows.
The 5th section, then, performs this function, and is the preparation for the reentry; this portion need not be any longer than 4 bars and works well when made up of 2 phrases each 2 bars long ending on the dominant chord which points to the home key.
Here the decision was made to employ some altered chords (dominant 7ths with raised or flatted 5ths) to create a smoother transition to the final entry of the theme with its chromatic harmony.
Some may find it more helpful, in settling on the exact harmony for this preparation, to first work it at the keys of the instrument as one would an improvisation, then go back and commit it to notation; we are employing here, after all, a system for improvising on a single free theme, and when the Prelude is finished in this form it should, after all, sound like an improvisation.
The final or 6th section is the reentry of the theme which typically, but not always, appears in the top line; here, In this example, the theme reenters in the soprano but instead of returning to the bright but somber home key of b minor the theme is worked in the luminous parallel key of B Major and harmonized chromatically, ending very softly, very quietly, in the radiant tonality of this key using a plagal cadence.
The Fugue subject enters first in the alto line of the home key of b minor; it starts on scale degree 5.
Many theorists teach that any fugue subject that begins on scale degree 5, or features 5 prominently in the beginning, will result in a tonal answer, because 5 must be adjusted in the transposition to begin a 4th higher, on scale degree 1, rather than on 2; then, following the adjustment, the notes of the answer are 5th transpositions of the subject; a real answer will occur when scale degree 5 does NOT appear prominently near the subject's beginning.
But here, instead of a tonal answer (which is expected, since the subject starts on the 5th scale degree) we find a REAL answer supplied ... in the tenor, in the subdominant.
Why is this answer real and not tonal? ... because here the 1st and 3rd quick notes of the countersubject make consonant harmony with the 1st long note of the subject which is being held on the 5th scale degree at the same time; the intervening 2nd quick note of the countersubject forms a major 2nd very briefly with the held note of the subject ... this interval is dissonant all by itself, but here the ear accepts it as a tolerable passing tone between the 2 notes on both sides of it.
Thus a real answer is pleasing overall to the ear and the listener does not sense an unprepared dissonance.
There's a lesson in this: a tonal answer DOES NOT always have to be supplied for a fugue subject which begins on the 5th scale degree, as some theorists insist; a great many of such subjects demand a tonal answer, but not all of them, not 100 per cent of the time.
Since the subject begins on the 5th scale degree, the answer, in compliance with common practice [See blog, Getting Started With Writing, Part XX], begins on the 1st scale degree, which necessitates e minor (the subdominant) as the key for the answer; a short transition (called a codetta, interlude, or link) of 2 additional bars are then inserted to produce a smooth return to the home key for the 3rd entry.
The 3rd entry then appears in the soprano as the 1st countersubject enters in the tenor and the 2nd countersubject in the alto;
The 4th entry is then in the bass, returning to the subdominant; here the 1st countersubject moves to the soprano and the 2nd countersubject to the tenor, with a free voice added to the alto, as expected, to complete the exposition in a 4 part texture.
The music then passes through a series of entries in A Major, f# minor, a minor, D Major, e minor, G Major, and a final entry in b minor; these various entries are separated by modulating episodes each 4 bars in length employing sequences built upon fragments of the subject or countersubjects and their inversions.
In the final entry the subject enters in the top line and undergoes imitation 2 bars later in the bass.
A coda of 5 bars follows in which the head of the subject is segmented in the bass; the music finishes in 7 voices employing a high F# inverted pedal point in the right hand approached by step from below; the final tonic chord with a raised (Picardy) 3rd is reiterated twice over a double pedal with the full power of the organ.
This final cadence is a bit unusual in that the 7th note of the dominant 7th chord leading into the final chord resolves upward by step rather than downward; this dominant 7th chord also has a raised 5th (to maintain agreeable harmony with the bass line).
This piece and the a minor Op. 25 Prelude and Fugue which precedes it chronologically share the same subject; that subject is inverted in Op. 26 and will repay careful study.
(con't in Part XXXIII)