A French verse form probably originating in the fourteenth century, but certainly derived from older Provençal forms. There is no set line length or rhythmic pattern for the ballade and although most writers would assume that the line length should be the same throughout, there are exceptions (some Ballades, for example, alternate four beat and three beat duple lines).
Early ballades are often of three stanzas of seven lines each, and an envoy stanza of variable length. Chaucer sometimes composed envoys which are the same length as his main stanzas, and sometimes shorter ones of five lines. The form is now usually written with stanzas of eight lines, though ten line stanzas are also known, and an envoy of four lines. (The …
Constable, John. "Ballade". The Literary Encyclopedia. First published 10 June 2002
[http://www.litencyc.com/php/stopics.php?rec=true&UID=1374, accessed 21 February 2017.]