During the last few years of his life, Schubert created a number of highly original sonata-form movements that radically reinterpret the form’s conventional elements and processes. In each case, the underlying cause of these innovations is the music’s concentration on one overriding issue—what might be called a “motive,” but in a broader sense than usual. This motivic idea arises from the voice leading of a specific, marked harmonic event and is expanded upon to become a dominant force in the form, affecting thematic structures, key relations and the general manner in which the movement unfolds.
From the perspective of William Caplin’s theory of formal functions, such movements are unconventional on all levels of their structure. Furthermore they challenge common notions about lyricism in Schubert’s sonata forms, specifically that his lyrical impulse is primarily melodic and divides the structure into “closed song forms” across the main and subordinate themes. In these later sonata forms, the initial impulse is harmonic and the resulting thematic structures are dynamic in character and open outwards to the movement’s overall process of motivic development.
The paper will look in detail at two examples—the first movement of the String Quintet in C major, D. 956 and the first movement of the String Quartet in G major, D. 874. In the Quintet, the initial common-tone diminished seventh gesture becomes the basic material of the entire exposition in a series of harmonic prolongations whose development disrupts local thematic structures and larger form-functional components. In the String Quartet, the opening slip from tonic major to minor initiates a process in which the tonic major-minor relationship and the relative major-minor relationship working in tandem determine the character, structure and motivic-harmonic make-up of the prime constituents of the form.