Czerny's foreword is a short paragraph that immediately suggests his attitude toward the subject:
The study of figured bass can only be of real value to the student if he learns to play all the chords in their many forms on the piano and is able to play them securely. The present work offers a contribution to that goal, in that the first nine numbers present the chords in block-chord form, and the remaining numbers the same chord repertoire in elaborated form, so that the student can be made more familiar with the various harmonic combinations. (my translation)His footnote to the title of the first section is decidedly more revealing: "The figures in all of these examples must be worked out by the student, who can avail himself if necessary of help from a textbook or a teacher." Thus, Czerny is really offering a practical diatonic and chromatic chord primer, not a figured-bass textbook.
The first example is of interest here. It covers all 24 major and minor triads in a total of 13 bars. The upper most voice covers the distance of an ascending octave, C5-C6.
The pattern of thirds within fifths—C-a-F in bars 1-2—is strictly maintained throughout, and it charts a simple path through the Riemannian Tonnetz. Here is a fragment of a common representation of the Tonnetz, with arrows showing the starting path of Czerny's progression:
And here is the entire sequence, separated out from the diagram:
I should note, incidentally, that is impossible to maintain the close voicing in the right hand with anything other than a rising line. Analogously to suspensions, which tend to force voice leading down, relative (R) and leading-tone (L) relations force voice leading upward.
