The list of Mozart's compositions in a minor key is short. Two piano sonatas, one string quartet, two piano concertos, two symphonies, a string quintet and the piano quartet are works in a minor key. And of these nine works, four are in the key of G minor, Mozart's dramatic key.
The Piano Quartet in G minor is in 3 movements:
I. Allegro - Mozart begins the movement straight away with the first theme stated in unison by all 4 instruments:
II. Andante - The middle movement is in marked contrast to the dark drama of the first movement as the instruments take turns in this gentle music in B-flat major, the relative major of the home key of G minor.
III. Rondeau - In an even deeper contrast to the first movement is this music in the key of G major. The piano opens the movement with the rondo theme, all join in the second statement of the theme. The strings alternate with the piano throughout this movement, with all 4 instruments coming together to add some spice to it occasionally. Mozart adds variety by dipping into a minor key in a few places, but the music doesn't stay there long. The opening theme of the movement comes back one last time, and Mozart wraps up the quartet with a short coda.