Contemporary records show that Mozart gave no fewer than 22 public performances between February 26 and April 3, 1784. In this period, it should come as no surprise to discover that he chose to return to a grand and brilliant format in the composition of his Piano Concerto No. 16 in D major, K. 451. As with its nearest predecessor in the same key of D major, Concerto No. 5, K. 175, the concerto includes parts in its orchestration for trumpets and drums, always emblematic of a pronounced celebratory and public style in Mozart concertos. (An even earlier D major Concerto, listed as K. 40, the third of Mozart's 27 piano concertos, was in fact an arrangement of sonata movements by Honauer, Eckard, and in the finale, C.P.E. Bach.) No. 16 is, however, an altogether deeper work, both more passionate and vital in character, more structurally masterful, and with a slow movement of remarkable intellectual substance.
The first movement (Allegro) opens with a typically Mozartean march-like figure, evoking a rhythmic formula virtually identical to that which opened Concerto No. 13 in C, K. 415. Mozart was to employ the same solution again in a number of his subsequent piano concertos, notably Nos. 18 in B flat, K. 456, and 19 in F, K. 459. Mozart's solitary Piano Concerto in G, K. 453, differs only slightly in that it features a trill on the second note, though the generally purposeful demeanor of its opening is the same. The most arresting characteristic of the D major Concerto, K. 451, is its near-symphonic robustness and ambitious sense of scale throughout each of its three movements, and in this work, Mozart undoubtedly achieved a significant advance in unifying both symphonic and concerto genres in a new, all-embracing creative unity. Indeed, it may well be reasonable to suggest that the "modern" Classical piano concerto was born on March 22, 1784, the completion date which appears at the head of the manuscript. Although Mozart probably played the work himself soon afterwards, the copy he later sent to his sister contained one passage of the Andante in fragmentary form. He, therefore, sent her a substitute passage in richer harmonies, although on many occasions, Mozart's copies of concertos he played himself seem to have been at best sketchy, including just the bare outlines of themes upon which he would extemporize in performance. Listeners new to the work will find the bracing final rondo (marked Allegro di molto) especially powerful and dramatic, offering an affirmative summary of one of Mozart's most innovative middle-period piano concertos.