After thinking more about this, and with the many inputs from the list, I
offer the following:

First by popular I assume we are talking about the popular music of
our century, since there were jesters, and wandering musicians playing
"popular" songs from the Egyptians on.  So there is a wider issue "what
is the distinction between popular music of, say, the 16th, 17th, 18th and
19th centuries and the classical music of the same time.  But this thread
does not seem to be addressing that issue - that might be an interesting
thread but I will leave it to others to start it.

Bill Pirkle