So what's special about this? The traditional approach to the development section is to begin by destabilizing the tonality and putting one or more themes from the exposition through some harmonic changes and fragmentation. But Schubert does more of this in the exposition! Schubert's themes tend to be fairly complex, often consisting of ternary structures. The first theme begins with this phrase:
|Click to enlarge|
As Wikipedia notes, the second theme is more lyrical and in four-part harmony. The theme begins on the third measure of this excerpt, where it says pp:
|Click to enlarge|
What Schubert has constructed is a kind of reversal of some of the basic characteristics of the first movement sonata form. In Haydn, Mozart and even Beethoven, a harmonically stable theme is presented, often followed by another in the dominant and this exposition is followed by a development in which the harmony is unstable and wide-ranging and the theme or themes are broken up and sequenced. While Schubert does indeed have two themes, the second in the dominant, each theme contains a development section with fragmentation and harmonic instability. But the development itself has little actual development. Instead, it is a more calm contrast with the exposition and recapitulation. The development sounds rather Mozartean, in fact.
Another unusual quality is the extent to which the subdominant is stressed, not just in the coda, which is normal, but in the first theme itself. Finally, Schubert ends the movement with an unusual cadence. Instead of the nearly mandatory V7 to I (in A major an E G# B D chord followed by A C# E) he has, in place of the dominant seventh, this chord: B flat, D G#, which is an Italian augmented sixth chord, normally used to prepare the dominant. The effect here is to again, bend things toward the subdominant, D.
But enough talk, let's listen to the first movement of the sonata. This is Rudolf Serkin whom I prefer because, unlike most of the other clips available, he repeats the exposition: