Formes fixes

This is a collective designation for the three chief forms of late medieval French poetry and music:  ballade, virelai, and rondeau.  Their main period was the 14th century, under the poet-composer Guillaume de Machaut.  After 1450 they gradually declined in importance, being replaced by freer and more varied forms.  All three forms have a refrain, which, however, has an entirely different function in the rondeau from that in the two other forms.  The presence of a refrain as well as etymological considerations ("ballare," to dance; "virer," to turn round; and "rond," round) suggest that originally they may have been dancing songs.

Ballade

The poem usually has three stanzas, each of seven or eight lines, the last one or two of which are identical in all the stanzas, thus forming a refrain.  The form of the stanza is: a b a b c d E    or  a b a b c d E F  (capital letters indicate the refrain), a scheme that, so far as the music concerned, can be simplified as follows: a a b C (a = ab; b=cd; C=refrain).
The Ballade plays a prominent role in the work of Machaut, who treated it as a polyphonic composition of great refinement and subtlety.  His example was followed by the French and Italian composers of the late 14th century.  The form continued to be cultivated, though much more sparingly, during the first half of the 15th century by composers such as Dufay, and Binchois.
The Ballade form, without refrain, was adopted by the minnesingers under the name Bar.  The ballade is not to be confused with the Italian "ballata" form, which is entirely different.

Virelai

Also called "chanson balladee."  Consisted of a refrain (R) that usually alternates with three stanzas (S):  R-S1-R-S2-R-S3-R.  The stanzas begin with two rhyming versicles and close with a versicle paralleling the refrain.  The musical structure corresponds exactly to that of the poem, the two parallel versicles being sung to the same music and the closing versicle to that of the refrain.  The entire musical structure is A b b a A b b a A b b a A b b a.
This same form appears in a strict version in the 14th century Italian ballata and in modified types like the laude and cantigas.

Rondeau

In its simplest, 13th-century form, consists of eight short lines with a rather artificial repeat structure, line 1 being identical with lines 4 and 7, and line 2 with line 8.  Lines 1 and 2 therefore form a refrain that recurs in part in the middle and complete at the end.  Music is composed for the refrain only (line 1=a, line 2=b) and is repeated according to the scheme A B a A a b A B (capital letters indicating the refrain).  Of the formes fixes, the rondeau was the only one widely used after 1400.