The Piano Concerto No. 21 in C major, K. 467, was completed on March 9, 1785 by Wolfgang Amadeus Mozart, four weeks after the completion of the previous D minor concerto, K. 466.
The concerto has three movements:
1. Allegro maestoso; in common time. The tempo marking is in Mozart's catalog of his own works, but not in the autograph manuscript.
2. Andante in F major. In both the autograph score and in his personal catalog, Mozart notated the meter as Alla breve.
3. Allegro vivace assai
The opening movement begins quietly with a march figure, but quickly moves to a more lyrical melody interspersed with a fanfare in the winds. The music grows abruptly in volume, with the violins taking up the principal melody over the march theme, which is now played by the brass. This uplifting theme transitions to a brief, quieter interlude distinguished by a sighing motif in the brass. The march returns, eventually transitioning to the entrance of the soloist. The soloist plays a brief Eingang (a type of abbreviated Cadenza) before resolving to a trill on the dominant G while the strings play the march in C major. The piano then introduces new material in C major and begins transitioning to the dominant key of G major. Immediately after an orchestral cadence finally announces the arrival of the dominant, the music abruptly shifts to G minor in a passage that is reminiscent of the main theme of the Symphony No. 40 in that key. A series of rising and falling chromatic scales then transition the music to the true second theme of the piece, an ebullient G major theme which Mozart had previously used in his Third Horn Concerto. The usual development and recapitulation follow. There is a cadenza at the end of the movement, although Mozart's original has been lost.
The famous Andante is in three parts. The opening section is for orchestra only and features muted strings. The first violins play with a dreamlike melody over an accompaniment consisting of second violins and violas playing repeated-note triplets and the cellos and bass playing pizzicato arpeggios. All of the major melodic material of the movement is contained in this orchestral introduction, in either F major or F minor. The second section introduces the solo piano and starts off in F major. It is not a literal repeat, though, as after the first few phrases, new material is interjected which ventures off into different keys. When familiar material returns, the music is now in the dominant keys of C minor and C major. More new material in distant keys is added, which transitions to the third section of the movement. The third section begins with the dreamlike melody again, but this time in A-flat major. Over the course of this final section, the music makes it way back to the tonic keys of F minor and then F major and a short coda concludes the movement.
The final rondo movement begins with the full orchestra espousing a joyous "jumping" theme. After a short cadenza, the piano joins in and further elaborates. A "call and response" style is apparent, with the piano and ensemble exchanging parts fluidly. The soloist gets scale and arpeggio figurations that enhance the themes, as well as a short cadenza that leads right back to the main theme. The main theme appears one final time, leading to an upward rush of scales that ends on a triumphant note.