À mon chevet is a series of posts featuring a quote from whatever book is on my nightstand at the moment.
This dense, excellent book is more about the place of Beethoven's fifth symphony in the history of human thought and philosophy, rather than an analysis of the work's compositional history and structure. The reference to the yellowhammer in this passage is to perhaps the most plausible source for the famous theme that opens the symphony, the song of a small bird that Beethoven heard on his regular walks. It is not nearly as satisfying as my favorite story about the meaning of the theme, so good that it must be apocryphal, cited by Guerrieri at the end of his preface, as a handwritten addition to a copy of Anton Schindler's biography of Beethoven. When asked about the meaning of the opening theme, an annoyed Beethoven supposedly said -- one can only assume, to make the story perfect, singing his response to the tune -- "It means, 'You are too dumb'."
Of course, only the perceiving subject could know whether their judgment is concept free and therefore aesthetically valid, and Kant admits that the perceiving subject is an unreliable witness, often unaware that a perception of beauty is based on a concept. That makes it difficult to tell whether an aesthetic judgment can be universally valid, which is Kant's ultimate goal. We can all too easily fool ourselves into mistakenly believing that dependent beauty is free, as when Kant takes in a seemingly spontaneous concert:
"Even a bird's song, which we can reduce to no musical rule, seems to have more freedom in it, and thus to be richer for taste, than the human voice singing in accordance with all the rules that the art of music prescribes. . . . Yet here most likely our sympathy with the mirth of a dear little creature is confused with the beauty of its song, for if exactly imitated by man (as has been sometimes done with the notes of the nightingale) it would strike our ear as wholly destitute of taste."
In other words, we could consider what one thought to be a yellowhammer's song and consider it free beauty, only to have to backpedal furiously to dependent beauty once we realized it was only the opening of Beethoven's Fifth Symphony. In Kant's opinion, we were simply misleading ourselves from the get-go ("our sympathy" confused with the song's beauty).
-- Matthew Guerrieri, The First Four Notes: Beethoven's Fifth and the Human Imagination, pp. 91-92