The composer of the 'CONCORD' Sonata is Charles Ives, an American composer who lived from 1874 to 1954. He was a pioneer in musical modernism and is widely regarded as one of the most influential composers of the 20th century. His works often featured unusual combinations of instruments and styles, and his 'CONCORD' Sonata is considered one of his most important works. It is a four-movement work for piano that draws on elements of American folk music, hymns, and classical music.