The Concerto in D Minor Wq.23 (the Wq is an abbreviation for the name of the musicologist who in 1906 assembled the first catalog of Bach's music, Alfred Wotquenne) is written for keyboard, strings and continuo and is in 3 movements:
I. Allegro - The 1st movement is in a type of sonata form, and begins with an angular, quirky theme. This theme and other secondary ones that are related to the main theme are played by the orchestra alone. The piano then jumps in with the first theme. The piano takes center stage and is answered by the orchestra. These beginning themes are developed slightly, and this section can be thought of as the exposition. There follows a development section that expands upon the themes at length. The main theme keeps bouncing back into the picture until what amounts to a type of recapitulation begins. After further exploring of the themes, the orchestra has the final word and brings the movement to a close.
II. Poco andante - Music that strolls gently from the instruments in splendid contrast to the drama of the first movement.
III. Allegro assai - Bach returns to the mood of the first movement with a theme that leaps and then pauses after the leap, like the instruments need to catch their breathe. This leaping followed by a pause appears throughout the movement, along with brilliant passage work for the soloist. The soloist joins in the leaping and taking of a breath later in the movement as the music remains energetic throughout. After a leap shared by strings and soloist, there is a short cadenza for the piano and the strings have the last word with a sigh of exhaustion.