"Memphis"

I'd long suspected that the line "Changing my life with its freedom ring" in "Memphis" contained an allusion to something, and I finally placed it.  Ultimately, it seems to refer to the last line of the first stanza of "My Country, 'Tis of Thee":

My country, 'tis of thee,

Sweet land of liberty,

Of thee I sing;

Land where my fathers died,

Land of the pilgrims' pride,

From every mountainside

Let freedom ring.