Well, yeah, but you can learn a helluva lot without taking lessons. Some of the most useful stuff I know, I grubbed out on my own.

But Monteverdi revisited. . . . An advanced search in google.com, putting in "dominant seventh chord" +Monteverdi came up with several websites, including this one. It contains the following:—

"Ancient Chinese and Greek musicians discovered the natural harmonics, and the scales of all cultures were derived from those harmonics. They also discovered that fixed tone instruments cannot freely modulate to all musical keys when so tuned. In the middle ages musicians began tempering their keyboard and fretted instruments to allow for some modulation. Tempered intonation is not in tune with natural harmonics.

"Keyboards and frets digitized musical intonation, dividing the natural continuum of tones into distinct points that were not meant to change. Skilled musicians loathed the aesthetic compromise. "The easiest (system) to sing," said Martin Mersenne in 1636, "is that which follows the natural harmonics." At that time, when Claudio Monteverdi introduced the dominant seventh chord, its dissonance was more sharply felt than it is today. When a modern, tempered orchestra plays Monteverdi, the contrast between true consonance and dissonance is obscured. Inversions, modulations, and other compositional resources have also been dulled by temperament." [emphasis mine]

This was essentially what Prof. John Verrall at the University of Washington School of Music said in class in 1957. He also said that Monteverdi got a lot of grief for one lousy passing tone over a dominant triad (incidentally, nobody was saying that Monteverdi wrote "sumer is icumen in;" what he did was write a madrigal arrangement of it). That Monteverdi's was the first semi-intentional use of the dominant seventh chord was reaffirmed by Prof. John Cowell of the Cornish School of the Arts in 1963 (according to my class notes).

I also found this on another website:— "What might look superficially like a dominant-seventh chord in Monteverdi is really a passing tone above the dominant triad. By the time we get to Corelli there are real dominant-sevenths, treated as chords not as counterpoint. What we ought to be talking about is not what we can name but what the names represent." Which seems to be saying, "just because you can put a modern name to it doesn't necessarily mean that that's what was intended at the time."

So, I dunno. . . .

Don Firth