I know that in the common practice style, even in free composition where guidelines don't apply strictly, a dissonant suspension must resolve. In the WTC 1 prelude in C major, bar 20 is a C dominant 7th, followed by the expected F. But, contradicting our expectation, it's an FM7 chord, keeping the leading tone at the top of the chord (where it happens to be harshly dissonant with the bass). This could be a 7-8 suspension (considered weak, but passable), but it never reaches F. Instead, it slides down chromatically to a diminished 7th in bar 22. Why did Bach do this, and does this technique have a term?
I would argue that there is a name for this phenomenon: the E is a chord tone!
Bach has a C7 chord in m. 20, but he decides to keep the E as a chordal seventh (creating a IV7) in m. 21. This is not at all unheard of in this style, and the added seventh dissonance just continues the tension and drive to the dominant that ultimately appears in m. 24.
But we can have our cake and eat it too, if we wish. Recognizing that this seventh is a dissonance with an urge to resolve downwards, there is a predominant prolongation in mm. 21–23. It ultimately moves from a IV7 to a ii half-diminished 6/5, meaning that this E does resolve down to D as expected; it's just delayed by the E♭ over the F♯.
Yes, I would say this can be called an unresolved suspension. The 7th, e, is prepared in the previous chord, but does not resolve upwards into f. Rather it moves downward to form a fully diminished 7th chord. This shows that the true target of the chord progression is to be found in m. 24, the dominant pedal point, while the f serves as subdominant, which is briefly tonicized. Bach was fond of the subdominant 7th, btw :)
...but it never reaches F.
Probably the most obvious way the
F could have been reached would be this...
But instead the
E4 is held and my first reaction when hearing that is an allusion to a sequence of seventh chords, here is an example in
That's fine, but begs the question why wasn't the
E4 resolved after that?
I think the essential dominant/tonic harmony of mm.20-21 is clear enough that it fulfill the two bar phrase patterning that started at m.6. Mm. Here are the last four iterations of that pattern...
In other words mm.20-21 satisfies as an iteration of the two bar phrasing pattern and the music can just continue on to the next phrase.
This is where I think an important rhetorical device is at work. Mm. 21-24 is a build in tension leading to the extend section over a bass pedal dominant. This is the climax of the piece. If m.21 had resolved the
F4 it would have been strong cadential harmony akin to a full stop, a period at the end of sentence. By not resolving that
E4, but yet fulfilling the two bar phrase pattern, the effect is more like a comma, and incomplete phrase that leads into the next phrase. Through this effect m.21 kicks off the build of tension toward the dominant pedal. It's a way to avoid a stop at a point where we really want momentum.
So, my way of looking at it is resolving
F4 would have been the pedantic thing to do. It would place formality over artistic effect. Instead, by holding the
E4 we get:
- an allusion to the sequence of seventh chords which is pretty in its own right
- a prolongation of tension that begins a dramatic progression to the dominant
Artistic choices like that are the difference between ordinary and extraordinary.
What is Bach doing?
This situation does not meet the definition of a suspension, since the resolution, by definition occurs within the "next" harmony. But it also doesn't meet the definition of a pedal point, because the harmony should resolve to meet the pedal point.
There is not a specific label for what Bach is doing here.
But let's call it a suspension
Since suspension is mentioned in the question, it's worth discussing as such, but stretching the definition so that the resolution can be delayed into a later harmony.
In that case, there are two separate issues, it's just that they are typically discussed as a single entity.
- Suspensions move downward by step.
- Dissonant harmonies resolve.
In a textbook suspension, one has, say, a V7 chord which moves to a I chord, but the dissonant scale degree 4 (the chordal seventh) is suspended into the I chord before moving downward to scale degree 3, a consonance. We typically learn this as a single idea.
But two things are happening: (1) the suspension is moving down by step and (2) the dissonant harmony (V7) is moving to a consonant one (I).
However, these can happen separately, and that is what Bach is doing.
As stated, m. 20 features a C7 chord, but in m. 21, the leading tone E, rather than resolving upward to F, is suspended — and does not resolve within that chord. (It can't, because neither Eb nor D would constitute a harmonic tone.) Instead, it moves downward in m. 22, to Eb, becoming the seventh of an F#o7 chord. This satisfies the condition that a suspension move downward to a tone that is part of the harmony, which itself happens to be dissonant. Bach maintains these tensions until the final measure of the piece. ("Tensions" rather than "dissonances", since there are some harmonies that are technically consonant, but don't feel like resolutions.)
There's a lengthy discussion of this here:
(But note the early comment: "You're getting some weird-ass answers here." :-) )
I wouldn't see much value in calling it a suspension, unless you want to call the E♭ on top of the subsequent dim7 chord another suspension... I'd look at it more in terms of voice leading causing the sort of 'crunch' we're more used to hearing in Bach's purely polyphonic works - no-one (I hope) goes through a Bach fugue trying to hang a chord symbol onto every beat of music!
I agree, the harmonic padding does create a surprisingly 'modern' flavour at that point. I'm sure most of us noticed and savoured that moment when we first played the piece.