Schubert's tonal networks are related to complex psychological meanings that point towards a no longer classical conception of the world: the world as chaos, not as kosmos.
The ﬁrst movement of the Sonata in C major D 840 is very powerful in its radical contrast between strength and sweetness. It’s tonal structure is beyond all norms: the second theme is not only in a minor key, which is already an exceptional fact, but it’s tonality, B minor, is extremely far from the main tonality. The second theme is presented in G major at the end of the exposure, for reasons of structural balance, but the normal exposure in G major does not attenuate the eﬀect of an unprecedented surprise of the exposure in B minor, moreover complicated by unpredictable modulations. Equally surprising is the link between development and re-exposure, which takes place without interruptions and is graduated in such a way that the listener is not aware of the passage from one section to another. In the re-exposure, the second theme is presented in A minor and at the end in C major. Even the closing Coda is unusually wide.
The second movement in C minor is certainly one of Schubert's most impressive tragic moments. The form is bitematic: ﬁrst theme in C minor, second theme in A ﬂat major, ﬁrst theme varied in C minor, second theme in C major, Coda on elements of the ﬁrst theme. A form with two themes so strongly characterized and (especially the second) rich of dramatic contrasts would suggest a development with the two opposing themes. On the other hand, the lack of development is typical of Schubert: the emotional content of the Sonata, which has become drama with the last Mozart and with Beethoven, tends with Schubert to be transformed into a tragedy dominated by Fate.
With its two complete movements, powerful and rough the ﬁrst, tremendously subtle of emotional content the second, the Sonata D 840 seems to bring Schubert's memory back to the Greek theater.
The use of diﬀerent tonalities involves a diversity, an individual character. This applies both to minimal variations of the constituent intervals, and above all as regards the timbre. Tonality are diﬀerent. The choice of a tonality therefore meant the identiﬁcation of a ﬁeld of feelings. The departure from a traditional network meant the opening of psychological spaces not, or rarely investigated. In the ﬁrst movement the second theme in B minor even introduces, with the change of the mode, a ﬁeld of opposite feelings. But the choice of B minor instead of for example G minor makes the transition even more dramatic. The Sonata was never completed. The Scherzo stops at the re-exposure, the ﬁnale stops during the development.
The incompleteness of the Scherzo and the Finale leaves many doubts about the meaning of this Sonata because the poetics of the ﬁnale contrasts with the poetics of the ﬁrst two movements. The incompleteness of the sonata D 840 therefore follows the non-solution of a problem that already appeared in Schubert's poetics, and which will be taken up again in the following Sonatas.