Fugue is a traditional polyphonic compositional technique in Western art music, whose methods were highly systematized by J. S. Bach in the 18th century. A fugal composition consists of multiple independent voices, where a subject is presented sequentially in each part, and motifs are skillfully combined and developed like a puzzle, sometimes expanded, diminished, fragmented, or even inverted and retrograded. It goes without saying that the most renowned fugues applied to keyboard instruments are J. S. Bach's two-volume The Well-Tempered Clavier. Although this work, composed of preludes and fugues in all keys, was not as widely known then as it is today, it was transmitted and used as teaching material in keyboard education up to Czerny's generation.

This collection of etudes was published in the same year as Czerny's edited version of Bach's The Well-Tempered Clavier. He likely composed this collection in the late 1830s, either concurrently with or very close to his editorial work on Bach's compositions. While Czerny added metronome markings, musical ideas, fingerings, slurs, and staccatos to his edited Well-Tempered Clavier, he similarly provided strict tempo indications, meticulous fingerings, ritardandos, and accent marks in Op. 400.

By the way, why did Czerny name this work 'Studies (Schule/Etude) in Fugue Playing' and position it as an etude collection, rather than simply calling it 'Preludes and Fugues'? In performing polyphonic music, including fugues, many unconventional fingerings are required, such as crossing the ring and middle fingers or continuous use of the same finger, in order to conform the fingers to the compositional technique. To freely grasp multiple intertwining voices with ten fingers, play at a fast tempo, highlight the subject presented in all voices, and translate the work's structure into sound, requires delicate and agile finger control, an analytical perspective to interpret the structure and character of the music, and strong sight-reading ability. All these qualities were educational aspects emphasized by Czerny, and Studies in Fugue Playing, Op. 400, enables their integration. According to Czerny's preface in the published score, due to the aforementioned performance intentions, the indications written into each piece (especially tempo and fingering) required careful attention. All pieces are fast in tempo, showcasing a superb fusion of contemporary pianism that maximizes the effects of the piano of that era—including hand crossings, leaps, octaves, and successions of thirds—and strict traditional voice leading. In this regard, this work is not only a compendium of technical education but also a major work that fully expresses Czerny's spirit as an artist rooted in tradition.

The collection consists of four volumes, with each volume containing six pieces, comprising three pairs of preludes and fugues. Unlike The Well-Tempered Clavier, it does not cover all keys, nor is there any particular intention discernible in the arrangement of keys. Many of the preludes are written polyphonically and take the form of character pieces or etudes of various natures. The subsequent fugues are often dense polyphonies whose subjects are frequently related to motifs from the preludes. Among collections of preludes and fugues, there is also a sister work in all keys, The Pianist in the Classical Style – 24 Preludes and Fugues in All Major and Minor Keys, Op. 856, dedicated to Liszt. It was also dedicated to F. Mendelssohn.