the ____ is an essential characteristic of sonata form

a. sudden crescendo
b. absence of harmony
c. fluctuation of rhythm
d. development of themes

is the answer d. development of themes

C or D. Definately not b and sonata does not necessarely mean crescendo so i think it might be d actually.

The characteristic of sonata form that is essential is the development of themes. To arrive at this answer, you need to understand what sonata form is and its basic structure.

Sonata form is a classical musical structure commonly used in the first movement of many instrumental compositions, especially sonatas and symphonies. It consists of three main sections: exposition, development, and recapitulation.

The exposition serves to present the main musical ideas or themes of the composition. These themes are typically introduced in different keys or tonalities to create contrast and musical interest.

The development section is where the themes from the exposition are explored, expanded, and transformed. This section is characterized by harmonic and melodic exploration, modulation to different keys, and various techniques such as fragmentation, sequence, and countermelody.

Finally, the recapitulation serves as a return to the opening themes from the exposition. The main difference is that in the recapitulation, all the themes are presented in the same key or tonality, typically the tonic of the composition. This section provides closure and resolution by restating and reinforcing the initial themes.

Based on this structure, the essential characteristic of sonata form is the development of themes. The development section is where composers showcase their creativity by manipulating, transforming, and expanding the musical ideas presented in the exposition. This allows for a deeper exploration of the themes and a richer musical experience for the listener.

Therefore, the correct answer to the question is d. development of themes.