Now here are the themes:
Exposition, first theme in orchestra, C major. Sorry, I have to patch this together because a six-measure phrase in the strings:
is answered by a two-measure phrase in the winds, making up an eight-measure sentence:
Had to cut and paste because of the way the score is laid out. Parts of this theme are varied and developed and then a new theme in the winds appears:
Then the original string theme returns, but this time in canon. Then another new theme appears with an ascending chromatic scale in the winds answered by a faster descending scale in the strings:
It is now around the 2 minute mark and the piano enters with yet another theme, this time an elaborate turn motif:
This becomes a long trill, under which the strings restate their first theme again. After some interplay between the piano and orchestra in which they share out the original theme, the piano has a solo with another new theme:
Up to now, this has all been in the tonic key of C major. But after a very brief tutti that confirms a modulation to G major, the piano has another solo with yet another new theme, this in G minor:
A little echo of the opening theme of the Symphony No. 40 in G minor there. After a brief transition passage we have a new theme in G major--my favorite theme from the concerto:
Then the original theme comes back, this time in the piano and in G major. After a considerable amount of flashy passage work in the piano first with sequences and then cadential, we have G major confirmed yet again with a big tutti on the original theme. This ends the Exposition. The Development begins with an orchestral transition that takes us to a half-cadence in E minor where the piano has a solo on a new theme in the new key:
There is a lot of passage-work for the piano using sequences that take us around a few different keys, but no significant new themes until Mozart works his way back, finally, to C major where the orchestra gives us a tutti with the original theme back in the original key of C major, beginning the Recapitulation. This is at the 8:23 mark in the recording. The orchestra begins a modulatory process that culminates with the theme in the piano in the new key of F minor. Then another modulation takes us back to C major where we hear that lovely theme I called my favorite, but now in the tonic key of C major. That is it for new themes as there is some more development using the themes we have already heard, the cadenza for piano and a final statement by the orchestra. And that's it.
By my count there are eight different themes in the first movement of this concerto, the two or three most salient of which get brought back in the Recapitulation. This is really a different kind of approach than we find in Haydn or Beethoven who are much more focused on one or two themes in a movement. But Mozart is remarkable in his ability to put this many different ideas together and make them into a natural sounding whole.
Let's end with listening to the whole concerto in a different performance. This is Maurizio Pollini: