Bach - Fugue in G minor BWV 578 modulation analysis

Dear reader, welcome to the new segment on beethoman.com – Modulation of the Week! This week will be dedicated to a quite special modulation. Certainly, the most conspicuous I’ve heard in the past two or three weeks. Actually, this modulation gave me the idea to form this section on the website. Ok, sweet talk is over, it is time for the analysis! Let me introduce you to Bach’s Fugue in G minor BWV 578.

Fugue in G minor BWV 578

This Fugue, as well as pretty much every Bach’s Fugue has many interesting aspects. However, today I will focus on one thing that really stands out and marks the modulation point. The main stars of the show are measures 10 and 11. In the measures which precede them, the dux (first appearance of the theme) was in the original G minor key, however its last notes modulated to dominant D minor where the comes began. Now, in measures 10-11, the comes approaches to its end and the musical flow should modulate back to its original G minor so the third voice could perform the dux once again. Modulations from D minor to G minor should not be a big issue, since these keys share many common chords. However, Bach would not have been regarded as such a genius, if he had been just an ordinary composer.

Example 1

Why is This Modulation Important?

Instead of creating a trivial modulation using any of the common chords, he used the whole new key as a transition one. Ambiguous C minor briefly takes place between the two opposed keys (G and D minor). In relation to the D minor, the C minor was introduced with the help of a diatonic modulation in which the tonic chord of the D minor became the chord of the ii scale degree in C minor. However, this is not the end of the surprises. After that, the musical flow introduces the dominant of the C minor, and one would think that the confirmation of the tonic comes next.

Nevertheless, the musical flow goes for the chord of the vio scale degree from the melodic minor, which is diminished, and alas, the C minor remains unconfirmed by the stable tonic function because the vio chord was also the modulation chord towards the original G minor. However, its function was fulfilled (Example 1)! And what a sounding effect it gave to the Fugue! Listen!

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What is your opinion about this kind of articles? Short and straightforward, would you like to see more of these in the future? Would you like to suggest some piece of music which I should analyze and represent to the people? Please tell me in the comments! If you’d like to see how this piece was incorporated into one of the power metal songs, click here. Until the next reading, stay safe and enjoy the music.

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