It's the chief danger faced by the composer when writing any organ music, particularly a longer work built upon a cantus firmus (c.f.), or fixed melody, such as a set of variations; this becomes especially acute when the plan for the composition makes it mostly non-modulating (where it remains in the tonic key throughout, save for perhaps only one or two very brief excursions into a related key).
We can avoid this danger by doing what's interesting or unexpected with each variation.
Someone doesn't necessarily need to hold a certificate or advanced degree from a recognized college or conservatory of music to write something compelling like this.
They don't have to have spent part their life earning their living as a musician.
They just need to know the basics about music theory, notation, scales and chords, how the Circle works, and what to avoid, be patient, doggedly determined, and have the guts to try.
It will help to print for yourself a copy of Variations Op. 4 and follow it along as you read through this narrative about how it was put together [See menu bar, Free Stuff].
If you start with a hymn-like theme, let's say, a c.f. 16 bars long made up of 4 phrases of equal length, you might consider writing a fanfare-like introduction using the melodic outline of the first 2 phrases of the theme in rhythmic transformation (same pitches in sequence but different note values); this would get the work off to an impressive start as it provides a strong sense of unity between the introduction and the statement of the theme.
If you begin your theme in a 4 voice texture, why not introduce it with something unexpected in the rhythm of the other voices from the get-go, such as triplets in the accompaniment; the listener finds something like this unexpected and arresting to the ear.
For the 1st variation you might try working the c.f. as a 2 voice canon at the octave with the right hand following one measure behind the left hand in a 3 voice texture.
You can even introduce a 4th voice, briefly, in this canon toward the end of the 2nd and 4th phrases of the theme, to interplay with the other 3 voices.
Your listeners won't expect this right off the bat, to start a big work with a strict 2 voice canon like this.
A famous example of this is Bach's organ Toccata in F Major, where he starts it, most unexpectedly, with an extended strict 2 voice canon at the octave in the hands over a held pedal note; no one would expect the opening of an organ toccata to begin with a learned (pronounced "ler'-ned) device like this, and it works amazingly well in the hands of this master of masters.
By stirring the sands of monotony this way, Bach succeeded in separating this work from the common and created something interesting and uncommon [ See blog, Do The Unexpected ].
After this, no one will expect the next variation to repeat this procedure, this time in a 4 part texture, switching the 2 voice canon at the octave so the left hand is now following the right.
That's exactly why you should do it.
For the 3rd variation you might consider restricting the c.f. to the tenor and bass lines but keep it moving between them, preserving a 3 part texture.
It's okay to dilute the formal rigor of which voice carries the c.f. here, as long as the result is smooth and pleasing to the ear.
You might then continue the 3 part texture, switch the theme for the next variation to the top line, start it there, then send it to the tenor or bass voice for every other measure.
Next, you might consider reducing the texture to 2 voices and make the theme disappear in figuration which suggests a harmony, forcing the listener's ear to search for it amidst a series of ascending arpeggios spread across both staves.
Following this, you might try staying with a 2 voice texture using a series of descending scalar passages interplaying with a simple bass motive consisting of an octave leap downward, still making the c.f. disappear in figuration.
After this you might return to a 3 part texture, have the c.f. return in the top line, and work it against a short, rhythmic motive reappearing in the bass on the even numbered measures.
On the next variation you might continue this procedure, this time having the same bass motive appear only in the odd numbered measures.
You might then create another bass motive moving in a dotted rhythm, have it appear on the even numbered measures, and employ ascending arpeggios divided between the 2 hands on the odd numbered measures, working it in a 4 voice texture.
You're already up to 9 variations here, and you've barely gotten started with your ideas!
Next, you might try something really bold, like introducing the the theme in inverse movement in the left hand, in another 2 voice canon at the octave, only with the theme entering right side up, in the right hand, if it will work.
This unusual procedure of juxtaposing a theme with itself in inverse movement in a 2 voice canon at the octave (provided it works and makes agreeable harmony) is a tricky business; we have to decide on a place for the 3rd free voice when the other 2 lines moving in canonic imitation happen to be very close together, are stationary, are moving in similar motion, or sounding octaves.
You're free here, to put the 3rd free voice either in the alto or bass and gradually nudge it along this way, your choice.
We may also find it necessary to exercise some discretion here [See blog, Poetic License] and tweak one note in the upside down version, as it is here, to get it to sound in more consonant harmony with the right hand.
In addition, when the canon is between the soprano follower (right side up) in the right hand and the tenor leader (in inverse) in the left hand, and the inverse enters the alto range, it will need to be divided between the alto and tenor voices.
In situations like this the tenor will take over playing a free voice for a few beats in those places until the inverse theme can return again to the tenor range.
Again, it's perfectly all right to dilute the formal rigor here as long as the result is smooth and pleasing to the ear, which is our guide for everything; if we can get it to work at all, it's quite an accomplishment.
It's in fact advantageous to take these kinds of liberties because it's another means of varying how we're presenting the theme, which is the whole purpose of writing or improvising variations; there's no shame in being bold like this [See blog, Getting Started With Writing, Part VI].
Having introduced the c.f. in inverse movement this way, you might then bring it more to the fore by moving it to the top voice and introduce it against running notes in the left hand.
You might quicken the tempo slightly here, start it in 2 voices, then add the 3rd voice a few measures later, as the momentum builds.
Up until now your piece has been non-modulating, but here you might decide to work the 2nd half of the c.f. in the parallel key (c minor), returning to the tonic key (C Major) for the next variation by means of a short transition.
Now, to really stir the sands of monotony that will set this work of yours apart from the common, you can try following this with a 4 voice fugato by using the upside down version of just the 1st phrase of the c.f. as a countersubject to a 2nd theme in faster notes made to blend with it and serve as its rhythmic complement.
This fugato variation would proceed as with a standard 4 voice fugue exposition and perhaps continue on for a few bars until everything comes to an unexpected, complete stop on a 1st inversion Neopolitan triad (the so-called "Neopolitan 6th chord" -- a major triad constructed on the lowered 2nd scale degree).
After a pause, the final variation may then proceed in the home key.
In this fugato variation it would be good to plan the entries in this order: tenor, alto, soprano, bass -- an order which seems to amplify the effect of a crescendo as the voices begin to pile up; J.S. Bach employed this effect many times in his fugue writing, as is clearly demonstrated in his famous organ Fugue in G Major ("jig").
The companion subject, in this scheme, would enter in the tenor and be answered in the alto, with the tenor continuing with the countersubject (inverted c.f.).
The countersubject (inverted c.f.) would then shift to the alto on the 3rd entry as the companion subject shifts to the soprano and a free voice is assigned to the tenor.
When the companion subject enters the 4th time in the bass the soprano would continue with the countersubject (inverted c.f.) and 2 free voices would be carried in the alto and tenor.
Since this fugato should sound like it belongs to a set of variations and not like an independent piece, it would be better not to follow this exposition with any episodic material; all that's required is to connect this exposition with the big Neapolitan 6th chord by means of a couple more entries.
For one of these additional entries the countersubject (inverted c.f.) might remain in the soprano with its companion subject shifted from the bass to the alto, assigning free voices to the tenor and bass.
Finally, there could be a brief modulation to a related key here, such as the subdominant, for the sake of variety; the countersubject (inverted c.f.) might then be inverted and made to enter in the bass as the soprano carries the companion subject and free voices are assigned to the alto and tenor; this fugato variation would therefore fittingly play out by recalling the c.f. right side up.
What has just been described is the common practice, orderly way of writing a fugue exposition -- the subject always enters with each new voice and the countersubject always follows immediately on the heels of the subject in whatever voice it enters.
But something else may be tried here -- a variant which would not be permitted in a conventional fugue; everything would be identical as before, save for the 3rd and 4th entries, which would be contrary to common practice.
In the 3rd entry the subject and countersubject might remain right where they are, i.e. reiterated in the alto and tenor, while a 3rd free voice would simply make its appearance in the bass; the subject might then enter in the soprano at the 4th entry and the countersubject in the alto as 2 free voices are assigned to the tenor and bass.
If the composer has written it both ways and is reluctant to abandon this variant, then it still might be inserted into the score; the bars having the common practice 3rd and 4th entries would be written into the score first and marked accordingly with a continuous straight line above the top staff.
The 8 bars having the variant would then follow this in the score and could also be so marked with another continuous straight line above the top staff; both sets of 8 bars might then be set off with double bar lines to indicate their boundaries.
The performer is granted the freedom here to decide how they wish to perform this 12th variation, i.e. whether to ignore the variant, select only the variant, or even play it both ways at the same time (which is not recommended).
This music is written to harmonize all 3 ways and would be theoretically playable whether the performer was playing to, trying to reach, and connect with mostly conservative or mostly liberal audiences.
The variant, when included in this fugato, sounds like a pair of redundant entries super-added to an otherwise complete 4 voice exposition, with the soprano line resting for 4 bars in the first of these redundant entries.
Single redundant entries are rare in fugal procedure, but they do occur with some frequency; having 2 of them is pretty much unheard of; having 2 of them where one is a voice short of the full number would be really off the wall.
This sort of proceeding is beyond daring and can be expected to have every cantakerous wig-wearing cantor and schoolmaster in Leipzig ready to tear his wig from his head and throw it at any of his scholars for even thinking it -- definitely not to be looked upon as a functioning norm.
NOTE: The author's preference is to either ignore the variant or select only the variant, then make a splice, but there's a great lesson to be found here. We discover, by listening carefully to the variant, that it also seems to grow naturally out of the 2nd entry. Typically, in writing the opening exposition of a fugue, the rule is: ONLY orderly entries are allowable -- but here, with this variant, we have an illustration, that breaking a rule or deviating at times from the norm of common practice can lead a composer to find beauty where they were told, or led to believe, that there was none. It's important to remember that the rule book of common practice norms which has come down to us from the work of countless Western composers down through the centuries is and always has been a friend who's there to guide and serve composers of the present day -- not to intimidate them, not to enslave them, not to be poised ready to crush them in an instant for the slightest deviation [See blog, The Rule Book, Getting Started With Writing, Part XX].
A stream of chords moving in parallel motion is commonly known as "planing;" chromatic planing occurs when such planing moves in half steps, ascending or descending.
If part of the c.f. happens to work with chromatic planing in the accompaniment, it would lend an interesting twist on this last variation; the melody in this case would probably need to be tweaked a little, with some of its notes moved perhaps to a different octave, to accommodate such a harmonization and to avoid some nasty dissonances, but, if it manages to work, it can be extremely effective [See blog, Marching, Your Ideas].
You might then round it all off by creating a short coda, working the 2nd theme in imitation at the octave again, this time in a related key such as the subdominant (F Major) and ending on a reiterated tonic chord, let's say in 7 voices, under an inverted pedal point in the top line using the full power of the instrument.
By going back and incorporating triplets in your introduction, there will be a rhythmic connective between the opening fanfare and the accompanying figure in the theme which follows, since you're using triplets there.
You might also consider introducing a melodic connective in this introductory passage by working the theme here in rhythmic transformation in big chords in the right hand against a moving bass line built upon the first few notes of the theme.
The c.f. when it immediately follows will then seem to evolve naturally from the introductory material.
If the introduction is energetic, and you feel the need to apply the brakes and reduce the energy level a little bit before the c.f. is presented, you might insert a pause, then include some slower chords at a reduced dynamic built upon a bass line using the first 3 notes of the c.f., pause on a discord, then begin.
This was the general scheme of variety within unity which was followed when Variations Op. 4 was written.
It takes guts to attempt or even contemplate doing something like this, but in the end the rewards of trying are infinitely greater than never trying at all.
As the old saying goes, there's still plenty of good music to be written in the key of C Major, but the best advice is: don't try to make every composition a masterpiece; instead, write as a method of learning -- write and write, and write some more, in order to learn from the process.
Seek not perfection at every turn; perfection is the art killer.
Strive for excellence instead.
The rest will come.