Anyone attempting to take seriously Carl Czerny's guidelines for musical performance must come to terms not only with what give every appearance of being definitive principles, but also with Czerny's own apparent contradictions of some of those principles. Although, as we will see, there is no denying a degree of inconsistency in Czerny's work—perhaps inevitable in so productive a career—a closer examination of one such case reveals considerable subtlety. Czerny's apparent inconsistency, I will argue, is in fact evidence of a sophisticated concept of the musical work in performance.

The principle in question is one of Czerny's most sweepingly formulated. In his “On the Proper Performance of All Beethoven's Works for the Piano” of 1846, Czerny's “general rule” declares that in the performance of the works of “all classical authors,” the performer “must by no means allow himself to alter the composition,” and adds even more pointedly that “in those keyboard pieces which were written for the five-octave instruments of former times, the attempt by means of additions to use the sixth octave is always unfavorable; likewise all embellishments, mordents, trills, etc. that the author himself has not indicated, however tasteful they may seem in themselves, justly appear superfluous.”

According to Czerny, Beethoven's scolding after his former pupil's fanciful performance at Schuppanzigh's “more than anything else, cured me of the craze for taking liberties of any kind when performing his works.” That was probably in 1816. But what are we to make, then, of his 1829 edition of Beethoven's Rondo in B Flat, WoO 6, for publication by Diabelli? The Rondo, from 1793, is the original finale for the B-flat Piano Concerto, Op. 19, and shares with the Concerto a five-octave compass: as is so often the case with Beethoven's early compositions, the high F is not only never exceeded, but is even used as a pedal tone at the top of the highest textures.

Given Czerny's “general rule” and his explicit remarks about range, we might reasonably expect that in filling out what little of the piano part remained unfinished, he would have preserved the five-octave compass of the piece. But instead he made full use of the sixth octave, as, for instance, in example 8.1b.

And given his proscription of added embellishment, we might expect him to have reproduced only Beethoven's original ornaments.