In the exposition, Brahms shows how an inverted form of the main theme meshes well with the closing theme. In the instance below, the inverted main theme is in the bass, while the closing theme is in the treble. Eight measures later, he swaps their registral positions.
In the development, Brahms shows how the closing theme can be well combined with itself in canon at the octave a half-measure later. In the instance below, the dux (leading voice) is in the treble, while the comes (the imitating voice) is in the bass. Eight measures later, he swaps their registral positions.
What Brahms never does in the symphony is combine these two instances of two-part counterpoint into an instance of three-part counterpoint, which works quite well in forming seven complete triads while maintaining independence among all three voices. One possible version, transposed to the key of the symphony, is below.
