The Exposition of Mozart's String Quartet No. 15 in D minor consists of the first 41 bars of the movement. This Exposition is, of course divided up into a FTA and a STA (First and Second Tonal Areas). The FTA is from bar 1-14, and at this point the FTA transitions independently (with no previous themes) to the STA until bar 25 when the STA begins. Overall the FTA can be broken up into pairings of aa and bb in terms of phrases, which end up being short, around 4 bars. For example, a from mm. 1-4 is repeated from mm. 5-8 though with different voicing (a'). Measures 9-14 become a bit more irregular, especially with the 2 bar phrase mm. 9-10 which ends on an A major triad (V).
The FTA is expectedly in D minor (i), while the second tonal area overall is in its relative major, F major. The STA can be characterized by much faster, staccato sextuplets that each voice takes turns propelling the entire ensemble. While the FTA can be characterized as far more melodramatic, with chromaticism and many contrasting dynamics, the STA moves more horizontally with no dynamic markings for multiple measures at a time.
The transition between the two tonal areas is distinctly chromatic, with lots of syncopation that both help smooth the transition to F major.
The development section, which begins in measure 42-70 expectedly toys around with the themes of the first two tonal areas in the exposition. There is no real distinct tonatlity to the development predominantly because of the abundance of chromaticisms and flirtations with leading tones and such.
Finally, the recapitulation which comes in measure 70-end rather suddenly is the capo of the piece verbatim. As the FTA of the recap (d minor) ends in measure 83, the transition this time, is actually a dependent transition, because it uses themes throughout the entire movement. In measure 94, the STA is repeated, however in the key of D minor (i) instead of F major (relative major). This is expected, since we know that the piece will end soon, and it needs to be in the true tonic.
The biggest thing to convey in performing this piece is the contrasting moods between the FTA and STA themes. While the FTA is quite somber, the STA hurries forward especially with the rapid sextuplets. Particularly at the end of the piece when the STA area is in D minor instead of F major, it is important to make this interesting variation clear.