What is "esquisses"

Esquisses (Sketches), Op. 63 is a set of 49 short piano pieces by French composer Charles-Valentin Alkan and published in 1861. The pieces are divided into four books; the first pair of books and the last pair each comprise between them pieces in each of all the major and minor keys. Book 4 ends with an extra, unnumbered, piece, Laus Deo, in C major.

Unlike many other of Alkan's pieces, such as the Op. 33 Grand Sonate and the Op. 39 set of etudes in all the minor keys, these 49 pieces do not focus mainly on virtuosity and transcendentalism and instead contain more of Alkan's sentimental and evocative writing. Alkan's innovation is also vividly present in the pieces. The 45th piece, Les Diablotins, features wrenched cluster chords and the 48th piece, En Songe, is a dreamy and quiet piece all except for the very final chord, which is a sudden F major chord with the dynamic ff. The 39th piece, Héraclite et Démocrite, features two sharply contrasting themes for the respective philosophers, and at some passages Alkan overlaps the themes to create a solemn and sad theme in the left hand and a bouncy and joyous theme in the right.