folk ballad vs folk music

folk ballad and folk music both are nouns.

Word	Noun	Adjective	Verb	Adverb
folk ballad	Yes	No	No	No
folk music	Yes	No	No	No

As nouns, folk music is a hypernym of folk ballad; that is, folk music is a word with a broader meaning than folk ballad:

folk ballad: a song that is traditionally sung by the common people of a region and forms part of their culture
folk music: the traditional and typically anonymous music that is an expression of the life of people in a community

Other hypernyms of folk ballad include song, vocal, ethnic music, folk.

folk ballad (noun)	folk music (noun)
a song that is traditionally sung by the common people of a region and forms part of their culture	the traditional and typically anonymous music that is an expression of the life of people in a community