The third type of evaded cadence is often referred to as Motivo di Cadenza.
In order to understand this concept, let’s look at an authentic cadence and it’s essential voice leading – 7-8 (descant clausula), 4-3 (alto clausula), and 5-1 in the bass (bass clausula)
Notice that the upper voices create a tritone that resolves (mi-fa in the natural hexachord and fa-mi in the hard hexachord)
If we then transform the next sonority into a cadential one by moving the C to B flat, we get the same structure, moving to F major, and the upper clausulae swapped
In modern terminology this would be analyzed as
Now lets skip the resolution sonority:
This is a quicker modulation moving down a fifth
If we replaced the chords on scale degree 5 with double cadences we would get the Motivo di Cadenza
Note that the Bb appears at the end of the first double cadence, thus obscuring the fact that it is a cadence.
Examples
The following is an example of a chain of double cadences moving down the circle of fifths from C minor to Eb major. The descant clausulae are notated in red, the tenor in blue (4-3-2-1), and the bass in black
Motivo di Cadenza (step 1)The next step is to anticipate the “fa” of the new key and avoid a full descant clausula. Notice how the end of the descant clausula ties into the tenor clausula of the new key.
Motivo di Cadenza (step 2)We can add a series of diminutions that incorporate an alto clausula (5-4-3)
Motivo di Cadenza (step 3)And add a directional diminution (to the 5) and in the bass
Bach – Prelude and Fugue No.7 in E flat major BWV 876 for Piano – Johann Sebastian Bach