This is my favorite period of Beethoven's work: during that brief time span he composed some two dozen sonatas, either for piano solo or with violin, starting probably with the Op. 17 Sonata for Piano and Valveless Horn, and continuing through the Opus 33 sonatas for piano. During this period he discovered the infinite variability of beats and repetitions.
Discerning this variability does not come easily to people schooled in reading first, feeling later. My need for variability is inborn. It infuriates some people. My son, a gourmet baker, cannot fathom my baking habits of throwing in a handful of this, a dash of that. He does, however, enjoy eating the result.
He and I have been collaborating on the Op. 17. Schooled as an orchestral hornist, he is in the at first uncomfortable position of having to measure things in handfuls and dashes, as a solo player has no choice but to fool around with the exactitude of beats -- when they begin and end -- and of runs -- taking command of them at every successive sixteenth note.
Until composing this post I had not noticed the parallel. But before working on this piece, with which until now I was so unfamiliar that I didn't consider it real, I had not been so aware of this conflict so explicitly treated. I now consider Op. 17 the starting point of this most fascinating period in Beethoven's development.
Who knows? It might have been the horn, the instrument and its traditional role, that triggered the train of thought.