Whoa! Mozart's String Quartet in D minor, K. 421 ....
First Theme= m.1-8 (1-4, 4-8)
Transition= m. 9-24 (dependent)
Second Theme= 24-41 (24-33)
This movement is in D minor. At first, I thought maybe the random C Major chord in measure 14 was the second tonal area, but if you look at it, it's pretty tonally unstable after that random chord. Almost as if Mozart's saying "Come on Miffy, grab the corn puffs- we're going to Iowa!" ????? RANDOM! In measure 24, Mozart actually modulates to the expected area of III, F Major, the relative major of D minor. Typical of Sonata form. The reason I think this is the actual modulation is 1. it's more typical 2. it's more tonally stable than the C Major chord 3. Look at the motion after the modulation: I, I6, V etc. Mozart is establishing key.
These themes do contrast in ways other than just keys. For instance, the second theme has more rhythmic crescendos that switch between the voices. The character changes from having the melody in the FT derive from descending Octave leaps, to having a more step-wise melodic motion in the ST; giving the ST a naturally happier feeling. The transition preludes this happier feeling very nicely by giving the 32nd notes in the first violin in measure 23. So the whole quartet is pretty sad, maybe their socks didn't get a chance to fully dry in the laundry and their left toe is still feeling the after-effect. Until the first violin says in m.23 w/his 32nd notes "don't worry! pruny lint is in style this season, take off your socks!" To which, the whole quartet rejoices in the barefoot, linty bliss of F major. As a performer, I would make sure that these sections have stark contrasts and that the chord in m. 14 is a big surprise. The first violin also has the job of introducing happiness in measure 23, so he needs to follow the slurs and make it as cute as possible.
The end is better defined as a closing theme, because it's a little longer than what I would call a codetta and it has "themes" and motives of its own that are passed throughout the voices.
An example of a passage where a solo part is played while everyone else accompanies is measures 25-29, where the first violin has the melody. An example of a first violin/cello duet can be found in m.34-35. And an example of a motive being passed throughout the quartet can be found in m. 12-14.
Let's move on to the development, shall we? ( I know, I'm going out of order from what the book told us to do, but why do they have us do the recap first?) The development spans measures 42-70 and starts with a an Eflat Major chord. The first motive developed here, we first heard in the opening of the exposition. Remember the descending octave leaps? I guess somebody didn't find soggy toe lint so attractive...sad. This motive is developed through "flirting" with different keys. Ex: m. 55 with Csharps and m. 58 with Fsharps. Another developed motive is the dotted eighth, sixteenth- two eight notes rhythm. It reappears throughout the piece. Another motive we saw in the first movement is augmented a bit in the development. Look at m.25 in the first violin, now look at m. 59, it's the same idea, only with a half note beginning and the motive eliding into the next measure. The retransition begins in m.65. An example of solo/accompaniment is in the first violin of m.55. An example a passed motive is in m.67-69. An example of a first/second violin duet is in m.64-65.
The recapitulation is in measures 70-117.
First theme= 70-77
Second Theme= 94-102
Closing Material= 102-117
The entire recap is in D minor. This is possible by the recurring motive placed in the transition that holds the Csharp, the leading tone to D minor that is going to confirm the listener that at the cadence in 94, they are indeed in D minor. Ironically, this is the same motive used in all three sections by the first violin, initially in m.23. The entry of the second theme is different in the recap because it falls on the downbeat of measure 24, where as in the exposition, it came in on beat 3. The reason this is possible is because of the preparation leading up to this entry. In the exposition, there was a lot of syncopation leading up to the second theme. In the recap, Mozart starts to place longer note values on the downbeats to emphasize meter and lead to greater unification as we reach a cadence and the end of the piece. For the rest of the recap, the rhythm is shifted forward to emphasize downbeats and the buildup of a cadence. This is especially apparent in the cello, where almost no emphasis of meter existed in the exposition until the double bar. In the second theme and closing material of the recap, the cello really helps to emphasize rhythmic stability to move toward the end of the piece. Mozart's writing here can be analyzed historically through careful thought of the classical era and enlightenment's role in influencing art of this time. Enlightenment philosophers would have said that the world is in order and harmony and would have placed much focus order and laws with an optimistic perspective of the world. Hence Mozart's orderliness, and need to establish order near the end of the recapitulation. The end of the recapitulation is designed to be able to repeat through the constant motivic repetition throughout the voices. This motion give the listener the idea that maybe the end is not quite there, perhaps more material may be introduced. The performers may choose to play it either way, Mozart probably designed it that way to add some enlightenment optimism and to ensure a longer piece so that the dinner party could last longer and get rich people more wasted and convinced to give him more money. The movement ends with a strong D minor PAC on forte.