When the orchestra plays in two keys at the same time?

When an orchestra plays in two keys at the same time, it is called "polytonality." This technique creates a rich, complex sound by layering different harmonic structures, often leading to tension and dissonance. Composers like Igor Stravinsky and Charles Ives have effectively used polytonality to enhance emotional expression and create unique musical textures. This approach challenges traditional tonal relationships and allows for innovative musical exploration.