Which characteristic defines Copland's musical style in works like 'Appalachian Spring'?

The correct choice highlights Copland's ability to evoke a profound sense of place and nature, which is particularly evident in works such as 'Appalachian Spring.' This composition draws inspiration from the American landscape and rural themes, embodying the characteristics of American folk music and tradition. Copland's style often integrates elements that reflect the expansive American experience, whether through depicting the vastness of the landscape or capturing the essence of specific regional cultures.

This approach allows listeners to connect emotionally and culturally, as his music often resonates with themes of Americana and pastoral beauty. The focus on this sense of place is one of the defining traits of Copland’s music, setting it apart from more avant-garde or urban-centric styles.

In contrast, the other options represent aspects that are not central to Copland’s style. For instance, while some of his contemporaries may have engaged with dissonance, Copland typically leaned towards more consonant harmonies that evoke warmth and openness. His works do not strictly adhere to European classical forms, as he often blended these with American musical idioms, and his thematic focus is more rural and pastoral rather than urban and modern.