Supplementary notes:

• Measures 1–4: The structural voice-leading of the opening is essentially parallel tenths, masked by doublings and the implication of the bass. Ironically, the more definite texture appears with the arrival of the contra-structural motive in measure 4.
• Measure 5: The vocal E of measure 5 originates as a passing tone from an implied F; leaping into this passing tone allows the contra-structural motive to take shape.
• Measures 9–12: The shape of the contra-structural motive more naturally belongs to C minor, toward which the music drives. The use of the Neapolitan in measure 11, however, allows Brahms to replicate the exact pitches of the original motive.
• Measures 13–7: The maintenance of D and B even as the music turns toward prolonging the relative major in measure 15 allows the continuation of the C minor version of the motive; this creates a linkage between phrases.