Sorry the guest above was me.

The term 'ballad' is itself an interesting one. Students of poetry may have encountered the term 'ballade', a name in prosody for a particular form of lyric poem believed to have originated in France and popular in the 14th century.

The term appears to derive from a word for 'dance', which suggests to me that rhythm was an integral part of the original form. Interesting that it came to be used specifically for narrative poetry, as well as for some traditional song forms.