Dear Michael,
I am sorry to state this, but in my Unequal Temperaments book, I pinpointed some very serious flaws in Duffin’s book. I am not the only one, temperament scholar Ibo Ortgies has also published negative reviews: I know of no single temperament scholar (the likes of Lindley, Rasch, Barbieri) who approves of Duffin’s book and other opinions about historical temperaments. Some of his statements are easy to prove to be false.
As for false statements (NOT by modern scholars AFAIK), they abound: Barbieri told me no long ago that any amateur feels entitled to publish outlandish statements on tuning and temperaments. It is not a recent phenomenon either. Montal (1828) in his great book on piano tuning observed that some published directions to tune the 12 pitches in Equal Temperament just recommended following the Circle of Fifths and tune every fifth … pure!!
Not to mention the seriously misleading works by Owen Jorgensen, debunked by many scholars as soon as they were published (starting in 1978), yet his books keep being read and quoted. His “equal-beating” modifications of historical temperaments, his testing historical temperaments basically on modern pianos . . .
Andrew please feel free to move this post elsewhere.