3) Q:  Just beyond this, you speak of “calibre,” which I’m not sure I understand either… Maybe not even a technical term, really?

A: Right. Think of firearms measurements.

4) Q: “The Sutherland solution” (and elsewhere “the Callas solution”) could use a line of amplification.

A: You’ll find extended analysis of Sutherland in Opera as Opera (indeed , she’s paired with Luisa Tetrazzini as exemplars of two great high sopranos with contrasting vocal structures), along with some of Callas. But in brutal brevity: Netrebko’s voice is not of the same calibre as Sutherland’s. Sutherland’s was substantially more voluminous, besides having freer emission, greater alacrity, and a longer extension, notably in the sopracuti range. No comparison, really. Consequently, Sutherland could sing long stretches of I Puritani or Lucia at restrained volume levels and still be tonally present in a large opera house, but when Netrebko did so, many phrases simply failed to register—they were audible, and pretty, but not present enough to hold us in suspense. Sutherland did, except at the outset of her soprano career, share with Netrebko an overall darkness of vowel formation—it was her most frequently cited demerit—and a relative weakness in the low range, despite her early mezzo identity. ^(I) But that was in the context of a voice of larger, longer format—the “option” Netrebko didn’t have, and the reason her Puritani, especially, would have been more convincing if she’d just sung out more of the time.

With respect to Callas, the contrast is even greater—a true dramatic soprano voice, at least at the outset, with an intense chest register and a far wider range of colors (some of them, unfortunately, symptomatic of the technical issues that contributed to her premature decline, but nonetheless intriguing for that). Again, there is no sensible comparison with Netrebko in terms of vocal size and bite, interpretive imagination, or individuality. Callas belonged in the Lady Macbeth/Tosca/Aïda repertory; Netrebko does not.

Q:  “[to take on these heavier roles] . . . she needs to access her full potential calibration by opening up a stronger chest connection, then solving the balance problems that arise from doing so.”

A: See above, except to note that if the chest voice had been further opened up (i.e., intensified—and only by working directly with a voice can one determine the point at which this becomes pushing past the instrument’s physical limits), the problem of correctly balancing and bonding it with the notes just above it would have presented itself in a new form, requiring further work. If the work is successfully completed, the result is a stronger, more interesting voice. If not, one is left with some version of the dreaded “hole,” or at best a weak link in the chain.