Why would somebody think you meant E Phrygian in that situation , rather than C Phrygian ? Because that ' s the way the phrase key of C , phrygian mode is generally understood today because of rubbish teaching . IOW , the lack of logic is due to not being aware of the terminology I mentioned before . If everybody used and understood the terms key of C , major mode and key of C , minor mode , then you ' re right it would be quite illogical to interpret key of C , phrygian mode as E phrygian . But we ' re not in a world of logic and knowledge . We ' re in a world where people think modes are drawn from a parent major scale , by starting on a different note . And that ' s all they generally understand about modes . As you mentioned in your other post , guitarists are the worst , because of crap guitar teaching . On the one hand guitar teachers some of them anyway promote the idea that modes are cool OK that they are a way of producing different moods when soloing on existing music largely false and on the other hand they then compound that by giving mode names to fretboard patterns crazy . It ' s all an obvious recipe for confusion . If I was a conspiracy theorist , I ' d say they did it all deliberately , in order to make more money from more lessons where they try and explain it all . But actually I think it ' s just incompetence . Loved your video , btw !