The only disagreement I'd have with that definition is that "commposed popular music" remains unchanged when it is taken over by a community. That is often not the case. All you have to do is listen to Charlie Poole or others doing popular music to see how much they've changed it. Once a community gets it's hands on a song, they shape it to reflect the culture of their community.
The "folk process" works equally well on composed popular music. That's true of much of the body of composed music. I see it in hymns, all the time. In some newer hymnals, the line in Amazing Grace:
   "That saved a wretch like me" has been changed to
   "That saved and set me free."

The folk process is just a scholars term for faulty memory.. :-)

Jerry