Uniquely this E flat major sonata does not start in E flat. It appears to start in a minor. Cadences are pretty ambiguous, however the first phrase of 8 measures long ends on a unison C. The next asymmetric phrase of 6 measures modulates to G major, and ends on a V/IV chord, making it a half cadence. That brief transitional phrase brings us back to a 4 bar recapitulation with the theme in A major this time? Two measure of staccato chords brings us to yet another key, and 8 measures of the A section. There is a key change at the end of this section, ending on a C major chord. This is the dominant in the new key of F major. Thus this piece is a rounded continous binary form.
The B section is the trio. This first period of this section comprises of two asymmetric phrases. The first ends on a PAC, the second lands on a HC, leading into the second half of the section. Not much too exciting happens, and I don't really care to go into too much depth. Interestingly enough, it appears to me that this section is more developmental, or possibly expositional. The first section appears to have much more transitional elements than the second. Regardless, the first section is much more tonally unstable, with many more phenomena, making each section a totally different character.
The structural phenomena in this piece are far too numerous to detail individually. Beethoven makes use of articulation, register changes, abrupt dynamics, ornamentation, and rhythm alterations. Some important phenomena include the striking F# in measure 4, staccato forte chords in measure 20, forte pianos, and change of rhythm in the trio. Overall, I really enjoyed this piece. It is a very beautiful largo.