Stringsinger [[ ...
6. Anything by Cole Porter, Jerome Kern, and George Gershwin and the old Broadway show writers. These tunes could never have been written communally in aural tradition.]]

Beg to differ - slightly. I think Gershwin's "Summertime" tune could have been conjured up in aural tradition (is it any more complex than "Greensleeves?"). And I think Jerry Bock did a great job of making such tunes as "L'Chaim!" and "Sunrise, Sunset" sound like they evolved in aural tradition.   Composers often borrow and bend tunes from folk or write tunes with similar chord progressions.    But when a full orchestra plays "Greensleeves" it ceases to be "folk," I'd say.