The Chromatic Fantasia and Fugue in D minor, BWV 903, is a work for harpsichord by Johann Sebastian Bach. Bach probably composed it during his time in Köthen from 1717 to 1723. The piece was already regarded as a unique masterpiece during his lifetime. It is now often played on piano.
An autograph of this work is not known. The musicologist Walther Siegmund-Schultze pinpoints the work to the "fermenting Köthen works" because of its improvisatory and expressive nature, using all keys. Because of its characteristics the piece became known as Chromatic, a term that did not originate with Bach.
The chromatic fantasia begins as a toccata with fast, up and down surging runs in thirty-second notes (demisemiquavers) and broken chords in sixteenth-note (semiquaver) triplets, which are often diminished seventh chords lined up in semitones. The second part is a series of very clear and remotely modulating soft leading chords that are written in the oldest copies as "Arpeggio", i.e. they require a spread chord. The third part is entitled Recitative and includes a variety of ornamented, enriched, highly expressive melodies. This part contains several enharmonic equivalents. The recitative finishes with passages that are chromatically sinking diminished seventh chords over above the pedal point on D.
The theme of the fugue consists of an ascending half-step line from A to C, here from the third to the fifth of D minor to the relative major key of F major.
