Beethoven’s Fourth Piano Concerto, to be played by Freddy Kempf at the final concert of his New Zealand Beetfest at Wellington's Michael Fowler Centre on March 14, was completed in 1806, six years after the Third. In the interim, the piano qua instrument had acquired new, higher notes, more volume (three strings per note) and more pedaling options (a mechanism enabling the hammers to hit one, two or all three strings). Beethoven took full advantage of the new options.
Beethoven himself was storming to new heights at this time—he premiered this concerto at the same concert, in 1808, at which his 5th and 6th Symphonies, Choral Fantasy and Mass in C were also introduced. Tragically, his advancing deafness meant this was the last occasion he could play one of his own concertos in public.
Everything I said about how the Third was an advance into full-blown Romanticism is true of the Fourth—on steroids. Expansive and expressive, boasting an epic tug-of-war in its second movement between piano and strings (believed by many musicologists to represent the confrontation by Orpheus of the Furies at the Gates of Hell), it is full of surprises, delights and sleights-of-hand: no orchestral build-up (the soloist actually kicks the piece off); imaginative and infectious melodies that appear in a variety of guises and keys; rhythmic subtleties that belie the simplicity of the time signatures; postponement of the unleashing of the full orchestra till the final movement; etc. Via his titanic intellect Beethoven gave arresting and theatrical expression to his volcanic spirit.
Here is the entire concerto played by Claudio Arrau, with Leonard Bernstein conducting the Bavarian Broadcast Symphony Orchestra:
And here is the final movement played by Freddy with the Bristol Ensemble: