No. 1: Allegro molto moderato, C minor, 4/4 time

This piece, positioned at the beginning of the collection of Impromptus, corresponds to a first movement in sonata form, if one were to liken the four pieces in the collection to a “sonata.” Therefore, this piece serves as a key to understanding its relationship with the sonata, as mentioned in the overview. Through a detailed formal analysis, we will elucidate Schubert’s compositional concept.

The piece opens with a forceful striking of G notes, layered in octaves. This is followed by a monophonic “question” and a harmonized “answer,” played four times in four-bar units. In this process, the eight-bar phrase is colored with different harmonies each time, as if illuminating a single object from various angles. This section, which began in C minor, eventually cadences in A-flat major, and a new section commences in A-flat major (mm. 42ff.). What is noteworthy here is that while the theme of the new section is recognized as the second theme due to its differing key and accompaniment rhythm from the opening theme, it is melodically derived from the opening rhythm of the first theme. In other words, this second theme possesses an affinity with the opening theme. After the second theme is repeated multiple times and builds in intensity, similar to the first theme, a new theme is briefly presented for eight measures in A-flat major from m. 74. This theme is named the third theme due to its new melody, but given the brevity of its presentation and its key, it can also be interpreted as a continuation of the second theme.

Following this, a five-measure transition derived from the first and second themes leads to a pause, meaning that up to m. 87 corresponds to the exposition if likened to sonata form. Indeed, with multiple themes presented and a modulation from C minor to A-flat major, it can be interpreted as sonata form (although not a relative key, the key relationship of modulating down a major third for the second theme is also seen, for example, in Symphony No. 7 “Unfinished,” D 759). However, because the first and second themes share the same melodic material, and the second and third themes share the same key, the three themes placed in the “exposition” are designed to have weakened contrast and to transition gradually. In this respect, the piece distinguishes itself from typical sonata-form movements where contrast is generated between themes. Consequently, it highlights Schubert’s unique characteristics, differing from Beethoven’s compositional style, which is marked by the “sublation” (Aufhebung) of two opposing propositions.

From m. 88, the first half is re-presented, paraphrased in a development-like manner. First, the first theme returns in the tonic key. Here, it is not only accompanied by the triplet rhythm derived from the second and third themes, but this rhythm also appears as repeated octaves, creating an effect of urgency. After the eight-bar theme is played twice, it deviates from the theme and builds in intensity. The second theme, originally in a major key, is recapitulated in G minor, adopting a new accompaniment rhythm of sixteenth notes and an off-beat bass line (m. 125), and the third theme returns in G major through an unexpected major-key shift (m. 152). Thus, while this section generally possesses the character of a development, what is actually played is nothing other than a recapitulation of the first half. It is evident that this piece is constructed more freely than a typical sonata-form movement, not only in its structure of merging development and recapitulation but also in its tonal design of the recapitulation. Avoiding contrasting elements as much as possible in the exposition, incorporating the character of the development into the recapitulation, and performing the recapitulation in free keys—sonata form is interpreted in a uniquely Schubertian way, and despite this piece being comparable to a sonata’s first movement, it is clearly differentiated from it. It can be inferred that this is why Schubert did not name it a “sonata.”

From m. 161, a coda based on the first theme begins. Here, the technique of interplay between major and minor modes, which Schubert favored in his later years, is employed to its fullest extent. This technique is foreshadowed at the moment the third theme is recapitulated in G major (m. 152) and is used even more vividly in the coda. The coda, which began in C minor, suddenly shifts to C major at m. 167. The combination of key change and sudden shift to pianissimo makes this one of the most striking passages in the entire piece, similar to the first song of Winterreise. Thereafter, C major is the primary key, but from m. 177, elements of C minor, such as E-flat and F-sharp, emerge, making the future of the major/minor mode uncertain. At m. 192, it seemingly settles into C major, but C minor is glimpsed through E-flat in mm. 194-195 and 199-200, and C major is finally confirmed only in the last four measures.

The overall tonal structure of the movement, broadly speaking, begins in C minor and ends in C major, thus appearing to align with the “path from darkness to light” (per aspera ad astra) structure popularized by Beethoven. In reality, however, the major and minor modes remain indistinct until just before the end, depicting a story entirely different from a clear-cut major-key apotheosis.

Reinterpreting sonata form while simultaneously defamiliarizing a linear musical structure through the interplay of major and minor modes—Schubert’s distinct direction, established after Beethoven’s death, is clearly discernible.