Jeremy Denk at the New York Review of Books:
If Ives’s music remains a source of doubt, doubt is also one of its great themes. The essential Ivesian gesture is an answer followed by a question. At a key juncture in the slow movement of the “Concord” Sonata, for instance, Ives builds to a climax on the famous four-note figure from the opening of Beethoven’s Fifth Symphony. In the wake of a thunderous C minor arrival, nearly inaudible wrong notes appear out of nowhere, “ruining” the achieved moment. They instill a double doubt, of understanding and perception; they represent harmonic uncertainty, but you also aren’t entirely sure that you heard them. The gesture feels almost comical at first, then acquires meaning: a delayed awareness of ambiguous overtones hiding in the clearest chords.
Many of Ives’s most important pieces are about blurred or doubtful perception. The beloved song “The Housatonic at Stockbridge” depicts a morning walk in haze and mist, while hearing a hymn from a church across the river. The loss of information, the disintegration of the tune, is essential to the beauty, like the crackle and hiss of old recordings: a failure that connotes authenticity.
more here.