Have been re-reading Vivian Perlis’ great book Charles Ives Remembered: An Oral history.
A piece that dates from 1906, In The Cage stemmed from a visit Charles Ives made with several friends to the Central Park Zoo, where they saw a leopard pacing restlessly back and forth in its cage. One friend joked, “Is life anything like that?” Ives transformed the quip into the short tone poem.
The song is essentially an epigram in music, built on radical new chords piled up in the interval of the fourth rather than the conventional thirds. Also remarkable is the repeated introduction to the piano part, a succession of chords of durations lasting (in terms of sixteenth notes) the sequence of 8-6-4-3-2-1. This shortening of the length of each chord has an uncanny claustrophobic effect. “The Cage” is one of Ives’ most effective ultra-short pieces. 
To my ears this has a most ‘modern’ sensibility to it: One sees skyscrapers, dirigibles and fast trains.
I’ve drawn much comfort from Ives over the years; certainly through his music, but also with many of the corollaries between his life and my own. Our homes are within ten miles of each other, and we both shared the benefits (and challenges) of being the sons of men who were themselves geniuses ahead of their time.
“Stop being such a God-damned sissy! Why can’t you stand up before fine strong music like this and use your ears like a man?”
– At a 1931 concert when a man booed during one his friend Carl Ruggles’s works
Ives was a musical genius, anticipating the serialism of Schoenberg and many other elements of modern music, such as microtones, by many decades. Unfortunately, this placed him squarely in the path of the conventional musical minds of his time. What frustration he must have felt reading reviews of his work, where instead of seeing the horizon line of a new art, the reviewer merely saw an amateur composer who just wrote down the wrong notes!
Ives had no patience for these people. On top of one review, he simply scribbled the phrase ‘rot and worse.’ To Ives, these were just mediocre minds, steeped in the traditions of the past. Problem was, they taught in the conservatoires, wrote the reviews and set the standards.
Ives assembled the Orchestral Set No. 2 from material composed circa 1909 to 1919. He derived some of the first movement, An Elegy to Our Forefathers, from an unfinished Overture to Stephen Foster. It is a haunting piece, with snippets of Southern Spirituals and other sonic folklore. At the end the listener can almost see old and long-gone spirits drifting in and out of view.