Leaving aside the allusions to Florestan and Eusebius, all of Schumann's proposed titles show some of the essential character of Op. 13's conception. This was of 'studies' in the sense that the term had assumed in Frédéric Chopin's Op. 10, that is to say, concert pieces in which the investigation of possibilities of technique and timbre in writing for the piano is carried out; they are 'symphonic études' through the wealth and complexity of the colours evoked - the keyboard becomes an "orchestra" capable of blending, contrasting or superimposing different timbres.
If etudes Nos. 3 and 9 are excluded, where the connection with the theme is tenuous, the etudes are in variation form. It was not the first time that Schumann had tackled variation form.[2] But here the variation principle is used more as free transformation, no longer of an actual theme, but of a musical 'cell' or cells (as for example in the same composer's Carnaval). The Études symphoniques learn the lesson of Beethoven's Diabelli Variations: the theme that acts as a unifying element is amplified and transformed, and becomes the basis from which blossoms inventions of divergent expressive character. The work also shows the influence of the Goldberg Variations, most obviously in the use of a pseudo-French overture variation, and in the use of various canonic effects.
The highly virtuosic demands of the piano writing are frequently aimed not merely at effect but at clarification of the polyphonic complexity and at delving more deeply into keyboard experimentation. The Etudes are considered to be one of the most difficult works for piano by Schumann (together with his Fantasy in C and Toccata) and in piano literature as a whole (Wikipedia)