How equal temperament ruined harmony (and why you should care)

An interesting and well-researched overview of the acoustical principles behind tuning and the various tuning systems that have existed in the Western musical culture prior to the current hegemony of 12TET. The title is, in my estimation, printed clickbait; the work doesn't make a solid case that equal temperament “ruined” harmony, but instead leaves the reader with the conclusion that 12TET is just one potentially valid option out of many, depending on context.

If you're a fretted string player or a pianist who has never had to grapple with the issues of 12TET before, portions of this book will be revelatory. Duffin pays a lot of attention to the minutiae of historical tuning systems, and these details may not have practical relevance or application outside of historical practice performance environments. There are also some issues with presentation; Duffin regularly interrupts the flow of text with biographies, some of them taking up a full two-page spread, and many of which contain information already present in the main text.