That Yates article (http://www.mustrad.org.uk/articles/blues.htm) makes what seems to me an extraordinary statement about blues origins and the concept of the blue note, but without footnoting it or even mentioning where he got the idea. He makes it sound as if it's common knowledge. Am I just not in the loop on this? Here's the statement:

African slaves, it seemed, had taken their own musical scales to the Americas. These were different from Western scales, and when the two scales met there were sound clashes, which produced so-called 'blue' notes.