He was influenced first by his father, a bandmaster who had libertarian ideas about what music might be. When he was perhaps 19 (the dating of his music is nearly always problematic) he produced psalm settings that exploit polytonality and other unusual procedures. He then studied with Parker at Yale (1894-8) and showed some sign of becoming a relatively conventional composer in his First Symphony (1898) and songs of this period. He worked, however, not in music but in the insurance business, and composition became a weekend activity - but one practiced assiduously: during the two decades after his graduation he produced three more symphonies and numerous other orchestral works, four violin sonatas, two monumental piano sonatas and numerous songs.
The only consistent characteristic of this music is liberation from rule. There are entirely atonal pieces, while others are in the simple harmonic style of a hymn or folksong. Some are highly systematic and abstract in construction; others are filled with quotations from the music of Ives's youth: hymns, popular songs, ragtime dances, marches etc. Some, like the "Three Places in New England", are explicitly nostalgic; others, like the "Fourth Symphony", are fueled by the vision of an idealist democracy. He published his 'Concord' Sonata in 1920 and a volume of 114 songs in 1922, but composed little thereafter. Most of his music had been written without prospect of performance, and it was only towards the end of his life that it began to be played frequently and appreciated.
(See Article Charles Ives' Musical Style)