The answer is yes: If one can posit an alternate universe that is in many recognizable ways congruent with ours, one must assume the existence of some congruent form of folk music. Of course, the farther the alternate world is from congruency, the less the chances of there being anything recognizable to us as folk music (which would also be true of any other recognizable facet of culture). There could be many scholarly treatises on the differences in similarity between the folk music of various universes based on the strength of the congruity to our own.

At some point, however, it doesn't matter if the non-similar civilization is in an alternate universe or merely in another part of this universe. Perhaps the slime creatures of a distant planet (or alternate universe) are having a discussion about the origin of a set of scent-poems and whether or not an odor with a known farter can be considered a folk smell. And then, of course, they could discuss different olfactorer's interpretations of the old smells and have an argument about whether or not they are flatulating them properly. To us it would just be a really stinky planet.