I think that GUEST Ripov in the 10 Jul 18 - 07:32 PM posting hit the nail with 'medieval nine pipe portative organ'. Such primitive instruments were limited to specific notes and modes are a result of that kind of limitation.

Few modern instruments are so limited. Fretted instruments such as the lute, and today the guitar, were never limited in such a way. Unfretted instruments like the viol family and the human voice, of course, were never so limited as well. I find it difficult to believe that 'vulgar' music always kept to such arbitrary rules.

In retrospect it seems that Modes were an attempt to rationalise technical imperfections. Such rationalisation is not necessary today.

So why are Modes still a source of anxiety today?

I blame it on jazz and higher education.

Round about the time when jazz went from 'good time music' to 'a pain in the ears' it flirted with modes. I'm guessing that it flirted with one or two of them only. That in itself would not have resulted in the current concern about the subject.

It has always struck me as amusing that Universities teaching 'Popular Music' include jazz in their curriculum. Sometimes as a mandatory subject. A problem for Universities teaching Popular Music is what to teach students who may well be more talented that their teachers. Modes and jazz will do nicely.

The fact that students would benefit more from playing in front of audiences than playing in front of teachers would not benefit a profession from which I am now safely retired.