I'm Dreaming of a White Yankee Doodle Stagolee!
One of the Ann Arbor District Library's outreach programs is Library Songsters, where a musician teaches K-12 students to how to write songs using information they learn in history or geography class. The students start to understand why the traditional songs they grew up singing are still popular a century or two after they were written.
There are whole books about one song: the seasonal White Christmas, the early American tune, Yankee Doodle, the ballad of a St. Louis barroom brawl, Stagolee, the folk/blues classic John Henry. New York, our most famous city, has more songs written about it than any other metropolis in America. The folk process itself is examined in volumes like American Roots Music and Making People's Music.