A Deceptive Mozart is Music to Our Ears
In music, a cadence is a harmonic sequence that creates a sense of resolution or pause. It is one of the most fundamental structures in music.
Mozart’s manner of preparing and executing cadences is unique to his compositional style, so much so that one might call such passages “Mozartian”.
In western tonal music, authentic cadences are the most common class of cadences. Consider, for example, the perfect authentic cadence (PAC) consisting of the final two chords of Mozart’s Piano Sonata №13 in B-flat major. The PAC is considered the strongest cadence because it generates the most complete sense of harmonic resolution for the listener.
Authentic cadences, such as the PAC, are pleasing to the listener because they resolve the harmonic instability that precedes them. They do this through a sequence from V to I (observed in the bass line), or dominant to tonic. The tonic (I) is the first note in the scale, and is the most important because it defines the harmonic relationships between all other notes in the scale. The dominant (V) is the fifth note in the scale, and the second most important. For example, in the scale of C major, the tonic would be C and the dominant would be G (a fifth above C).
The dominant is the second most important note in the scale because it is the first distinct pitch (other than the tonic itself) to arise from the overtone series of a vibrating string. When a string is plucked, it will vibrate at integer multiples of the fundamental (lowest) frequency, which is the frequency of the tonic. When we play a note on the piano we think of it as vibrating at one frequency to produce one note, but in reality the piano string is simultaneously vibrating at multiple frequencies, and therefore multiple notes, as determined by the overtone series. However, the majority of the amplitude of the vibration is in the fundamental, such that our ears perceive only a single note.
So, if the string is tuned to C, the fundamental frequency corresponds to the note C. The second overtone is 2 times the fundamental frequency. When the ratio of the frequency between two notes is 2, our ears perceive those notes as being part of the same pitch class. In other words, the second overtone is also a C, but one octave up from the fundamental frequency. This illustrates the concept of the register, or height, of a note. Finally, the third overtone is 3 times the fundamental frequency. The third overtone is 1.5 times the frequency of the second overtone. Our ears perceive a frequency ratio of 1.5 as a perfect fifth. Therefore, the third overtone corresponds to the note G, or the dominant in the scale of C.
Authentic cadences are structurally sound because they involve motion from the second to first most important notes in the scale.
Mozart’s music is filled with authentic cadences of varying strengths that, due to their naturally logical structure, are expected by the listener.
Fulfilled expectations are a key ingredient in musical composition. They provide a guiding framework for the listener and can give the most expansive works a fundamental structural coherence.
However, the violation of expectations is also what makes music beautiful. Unexpected departures from harmonic resolution allow the composer to prolong periods of harmonic instability and generate variety. When the “correct” cadence finally arrives, as it must, the conclusion can be all the more powerful.
Mozart often violates the listener’s expectations through his use of the deceptive cadence.
Consider the deceptive cadence at the end of Mozart’s Piano trio in G Major K. 496. First you will hear a few measures that end in a typical authentic cadence, with motion from V to I. The music then repeats itself; however, when we reach the cadence again, something unusual happens. The music intensifies, and instead of the expected motion from V to I, we unexpectedly move from V to VI. This leaves the music harmonically incomplete, and we are left with an unusual, yet remarkable sense of suspension. Very quickly after this “failure” to reach the tonic, the cadence is repeated and ends correctly as a true authentic cadence. You will notice that this final cadence is psychologically the strongest because it was prepared, or made necessary, by the deceptive cadence that came directly before it.
Note that a deceptive cadence does not necessarily have to move from V to VI (as in the above example) to avoid I, however this is the most common motion observed in music.
Although they may have similar structures, the deceptive cadences in Mozart’s works can exhibit greatly contrasting colors and expressive purposes.
The deceptive cadence at the end of Mozart’s Piano Sonata № 10 in C Major is an example of a deceptive cadence with a complex significance. On one hand, it presents the existential crisis of music which has forgotten its way and does not know how to end (as suggested by the long pause that follows). However, upon arrival of the subsequent perfect authentic cadence, that momentary lapse seems almost humorous; like a premeditated joke.
One of the most extraordinary instances of a deceptive cadence occurs in the second movement of Mozart’s Piano Concerto №23 in A Major. The melancholic solo piano passage that begins the movement is again repeated approximately two-thirds the way into the movement. Right when we think we are at the end, the moment when we return from V to I, the music instead moves to VI (you can see the soloist glance up at the orchestra in this moment). At this instant, the woodwinds and horns enter, also on VI, like a ray of light shining through the darkness. However, the cadence is again repeated, and upon return to I the entire orchestra enters in on the melancholic home key of f# minor, securing the music’s fate.