Except for the tarantella dance, the section of the text that we are dealing with is composed mainly of dialogue.  We decided that, for the purpose of simplicity, the oboe would represent Nora, the horn would represent Torvald, and the piano would mainly provide accompaniment, and occassionally represent Rank. 

Three basic methods convey the dialogue musically.  First, motifs - short figures repeated throughout the piece - represent ideas and objects in the scene.  The most central motif is that of Krogstad's letter, which is introduced in the first two measures by the oboe.  Second, different melodic and harmonic structures both reveal the characters' moods and set the general tone for a particular section of the piece. For example, in measure 23 of the last section (not shown here) Nora ends the letter motif on the major third chord for the first time.  This shows that her relationship with the letter has changed; now she views the situation with the letter as an opportunity for the miracle, which will save their marriage.  Finally, the instruments'  mimicking of the human voice is used to speak sections of dialague.  The most obvious example is when Nora calls: "Torvald!" - here the oboe uses a descending fourth, similar to the  a sound of the human voice.