A great TV documentary I have mentioned in the past here (I think!) is the "Howard Goodall's Big Bangs in Music" (BBC I think). He goes into considerable detail with visual examples of the 'perfect temperament to equi-temperament' historical voyage - his opinion is that it was the Piano Accordion that spread the 12 tone equi-temperament everywhere and wiped out other older 'perfect' style tunings.

(See - I mentioned Piano Accordions again!)