Exploring the nine-line stanza in Middle English is a good lesson in what sort of identities stanza-forms can have. If you search for nine-line stanzas in the Digital Index of Middle English Verse, you find 60 odd entries. About a third of the poems in this form are written by Charles d’Orleans, some of the many lyrics which make up his Fortunes Stabilnes. In French lyric verse, ballades are written in stanzas of various different lengths. Charles’s nine-line stanza ballades are merely one variation amongst a number of different stanza-forms which he uses for his ballades.