Since according to my search, there remains only one surviving example of this 13th Century French form, I will provide you with the commentary of my favorite extant sources, and a link to that actual work.
A french form that can’t make up its mind whether to be verse or prose. More seriously, it is a romance that alternates between the two.
Pasted from http://www.poetrybase.info/forms/000/39.shtml
My thanks to Charles L. Weatherford for his years of work on the wonderful Poetrybase resource.
Chante Fable is a medieval French drama composed with alternate sections of verse and prose. It was originally meant to be performed by two jongleurs, the verse was sung, the prose spoken.
Chante Fable verse is:
• in sections alternating verse with prose.framed at the poet’s discretion with no specific number of lines.
• syllabic, usually 7 syllable lines and the strophe ending with a line of 4 syllables.
• rhymed using assonance within the line in all but the last line.
Pasted from http://www.poetrymagnumopus.com/index.php?/topic/681-chante-fable/
My thanks to Judi Van Gorder for years of work on this fine PMO resource.