another perfect example of a modern folk song is scorn not his simplicity,it works very well sung unaccompanied,so stylistically it fits the description.
I stress that style is only one of the ingredients.
styles are also important in determining different traditions,for example arabic traditional music uses different melodic scales /notes to flamenco or irish music,it is these different styles of musical sound,that enable the listener to differentiate,between different roots musics or traditions,plus different styles of lyric writing.
if a song writer wishes to write a convincing modern english folk[FAKE TRADITIONAL] song written in an authentic style,he would be advised to study the styles of writing AND THE STYLES OF TUNES in CHILD BALLADS.