Yeah, I’m in agreement with you and others that it isn’t the most compelling example he could have chosen.
As to the enharmonic seam thing, that is indeed the point: you either have to cross the enharmonic seam by spelling two identical-sounding intervals differently (in this case, one of the major seconds has to be spelled as a diminished third) or else you have to deny the seeming aural fact of octave equivalence by spelling the return of C as B-sharp. Since composers are extremely reluctant to do the latter, they have no choice but to do the former—a commonplace in the nineteenth century, a bit of a special trick in the mid-eighteenth.
Yeah, I’m in agreement with you and others that it isn’t the most compelling example he could have chosen.
As to the enharmonic seam thing, that is indeed the point: you either have to cross the enharmonic seam by spelling two identical-sounding intervals differently (in this case, one of the major seconds has to be spelled as a diminished third) or else you have to deny the seeming aural fact of octave equivalence by spelling the return of C as B-sharp. Since composers are extremely reluctant to do the latter, they have no choice but to do the former—a commonplace in the nineteenth century, a bit of a special trick in the mid-eighteenth.