ITALIAN SIXTH CHORD

An Italian sixth chord is the chord built as a stack of the diminished third and major third, with the chord root on the raised fourth scale degree. It is easiest to recognize it as the diminished triad flat three chord on the raised fourth scale degree. This way, we can easily recognize it in a score using the standard procedure for recognizing chords i.e. after we put its notes in the form of stacked thirds. This is shown in the next figure which shows the Italian sixth chord in the C major key.

Figure: The Italian sixth chord in the C major key annotated with the improper chord annotation

Unfortunately, diminished triad flat three chord does not exist. 3 must not appear in altered tones of a chord (this was mentioned in chapter Altered, added and omitted tones). The only possible solution is to change the spelling of the chord. The next figure shows the Italian sixth chord in the C major key and in the position in which it appears most often. If we change the spelling from F# to Gb, we can write enh Ab7(no5). “enh” tell us that the used annotation is only enharmonically equivalent to the chord as it is written in the score.

Figure: The Italian sixth chord in the C major key

In the C minor key, the harmony annotation would be c: enh VI7(no5) and the chord annotation would be the same.

The resulting annotations are quite long and inconvenient. In the next chapter, we shall learn the harmony annotation for the Italian chord which is simple. However, there is no simple chord annotation for it. 

Annotating Italian sixth chord

The harmony annotation for the Italian sixth chord is It+6 no matter of a position in which it occurs. The next figure shows an example of the annotated Italian sixth chord in the position in which it appears most often. 

Figure: Annotating the Italian sixth chord

Italian sixth chord in major and minor key

The Italian sixth chord is the same in a major key and its parallel minor key, thus having the same note names, chord annotations and harmony annotations. This is illustrated in the next figure. 

Figure: The Italian sixth chord in the C major key and its parallel C minor key

We see that if the current key is a minor key, the Italian sixth chord needs only one altered scale degree, the raised fourth scale degree. However, if the current key is a major key, the Italian sixth chord needs two altered scale degrees: the raised fourth scale degree and the lowered sixth scale degree. This is the reason why the Italian sixth chord appears more often in music written in minor keys.

Similarity between Italian and German sixth chord

If we compare the Italian sixth chord and the German sixth chord, we see that they are similar. The Italian sixth chord can be viewed as the chord made from the German sixth chord by omitting one note. This is illustrated in the next figure. 

Figure: Similarity between the German and Italian sixth chord

Italian sixth chord usage

The Italian sixth chord most frequently resolves to a chord with the root on the dominant (the fifth scale degree). The raised fourth scale degree resolves up to the fifth scale degree while the sixth scale degree resolves down to the fifth scale degree. This is illustrated in the next figure.

Figure: Resolving the Italian sixth chord in the C minor key

Mozart’s Fantasia in C minor K. 475

We find the Italian sixth chord at the beginning of Mozart’s Fantasia in C minor K. 475. It is a very interesting composition that contains a lot of tonality changes (modulations). Although it is in the C minor key (and it ends in the C minor key), most of it is written in the C major/A minor key signature, and most of the modulations are not followed by a key signature change.

The next figure shows the harmony analysis of the beginning seven measures. We can recognize the Italian sixth chord in measure 2. It resolves to a chord with the root on the dominant. The German sixth chord also occurs in measure 1 and resolves to a chord with the root on the dominant.

Figure: The beginning of Mozart's Fantasia in C minor K. 475