The frontier of Impressionism was started due to the Romantic era (Eschman 157). In the Romantic era, the typical musical elements of rhythm, harmony, and melody were extremely important in music (Eschman 157). However, during the Impressionist era the significance of these musical elements became less important, and were outstripped by timbre and mood setting elements (Eschman 157). Due to how different this style was at the time, it became a frontier. In an analysis of the music theory of Debussy's music, he has a tendency to use unusual chords in situations where it would be more appropriate to use the triads of a key (Devoto 460). For example Debussy used an F major chord with a C at as the lowest note of the chord (Devoto 460)