What is the meaning of the "chiaroscuro" sound that was considered ideal in Classical and early-Romantic Italian opera?

Question

Apparently, in Classical and early-Romantic Italian opera (the "bel canto" opera repertoire), the ideal kind of vocal colour was a so-called chiaroscuro sound. The chiaro- part translates as "clear" or "bright", while the -scuro part translates as "dark".

However, no two different sources I've found agree as to what is actually meant by chiaroscuro. I have found interpretations along the lines of each of the following:

1. chiaro- refers to squillo*, while -scuro refers to the presence of "chest voice".
2. chiaro- refers to the presence of "chest voice", while -scuro refers to a low larynx.
3. chiaro- refers to the larynx being not too low, while -scuro refers to the larynx being not too high.
4. In terms of the aspect of perceived "brightness" or "darkness" of vocal timbre that relates to how much the larynx is (respectively) raised above or lowered below the most relaxed available position for the pitch being sung, chiaroscuro refers to "darkening" the timbre as you sing higher. So,
   • for higher notes, chiaro- refers to the higher pitch while -scuro refers to the darker timbre;
   • for lower notes, chiaro- refers to the less dark timbre while -scuro refers to the lower pitch.
5. A special case of number 4: chiaroscuro refers to a fairly constant absolute height of the larynx.

(Furthermore, one sound that I personally find quite beautiful is the combination of the "clearness" coming from a larynx that is in - or is at most only slightly lowered below - the most relaxed position for the pitch being sung, together with the pleasant "darkness" of a chest-voice-ish sound as in number 1. So I also wonder whether this might have been what the chiaroscuro ideal was.)

What actually was the chiaroscuro sound that was considered ideal in Classical and early-Romantic Italian opera? In fact, did this "ideal vocal colour" even exist, or is the whole thing just operatic folklore? And if there was much belief in an ideal vocal colour, was there ever a reasonably consistent view as to what the ideal vocal colour should be, or was there significant variety of differing opinion?

I would appreciate, please, if anyone giving an answer that claims to know what the ideal chiaroscuro sound was could back this up with reasonably convincing historical sources and/or citation of the research of experts in historical performance.

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*squillo apparently refers to the "ringing" quality associated with overtones within a certain range which some people take to be around 2-5 kilohertz (roughly A6 to E8) although others seem to take it to be a narrower subrange of this.

Answer 1

Are you sure that chiaroscuro necessarily relates to vocal timbre? Do you have a source that specifically makes that connection?

I ask because, in my experience, chiaroscuro pertained to other elements of the composition and production.

Most specifically, it pertains to the relationship between the more neutral (and perhaps static) recitative and the more elaborate (and often longer) arias. So if chiaroscuro was the highlighting of light against a dark background, so too would the aria be naturally highlighted against the more neutral recitatives that surround it.

And less commonly, chiaroscuro can indicate a production choice, like for example a dark set used to highlight a brightly clothed singer.

But again, my experience with chiaroscuro is almost exclusively connected to the alteration of recitative and aria. I'd be curious to hear your source that connected it to vocal timbre.

And speaking of sources, in my own library I see that The Story of Opera by James Parakilas agrees with my understanding of this topic. He also cites Piero Jacopo Martello's Della tragedia antica e moderna from 1715, of which there is a translated excerpt in both Opera: A History in Documents edited by Piero Weiss and Strunk's Source Readings in Music History. In the latter, we see:

Mind, however, that when you end a scene with an exit aria you do not begin the very next one with an entrance aria. That would rob the music of its chiaroscuro. The instrumental ricercate would tumble over each other and instead of helping would hinder the effect.

Thus chiaroscuro is really a formal concept, not a timbral one.