Virelai in the context of "Rondeau (forme fixe)"

The formes fixes (French: [fɔʁm fiks]; singular: forme fixe, "fixed form") are the three 14th- and 15th-century French poetic forms: the ballade, rondeau, and virelai. Each was also a musical form, generally a chanson, and all consisted of a complex pattern of repetition of verses and a refrain with musical content in two main sections.

All three forms can be found in 13th-century sources, but a 15th-century source gives Philippe de Vitry as their first composer while the first comprehensive repertory of these forms was written by Guillaume de Machaut. The formes fixes stopped being used in music around the end of the 15th century, although their influence continued (in poetry they, especially the rondeau, continued to be used).

The ballade (/bəˈlɑːd/; French: [balad]; not to be confused with the ballad) is a form of medieval and Renaissance French poetry as well as the corresponding musical chanson form. It was one of the three formes fixes (the other two were the rondeau and the virelai) and one of the verse forms in France most commonly set to music between the late 13th and the 15th centuries.

The formes fixes were standard forms in French-texted song of the fourteenth and fifteenth centuries. The ballade is usually in three stanzas, each ending with a refrain (a repeated segment of text and music).

The Chantilly Codex (Chantilly, Musée Condé MS 564) is a manuscript of medieval music containing pieces from the style known as the Ars subtilior. It is held in the museum at the Château de Chantilly in Chantilly, Oise.

Most of the compositions in the Chantilly Codex date from c. 1350–1400. There are 112 pieces total, mostly by French composers, and all of them polyphonic. The codex contains examples of many of the most popular courtly dance styles of its time, such as ballades, rondeaus, virelais, and isorhythmic motets. Some of the motets are rhythmically extremely complex, and are written in intricately exact musical notation. Two pieces by Baude Cordier were added at a slightly later date at the front of the manuscript, and use unusual shapes to reflect their musical contents. The piece "Belle, Bonne, Sage, Plaisant" (image right) was written to a special lady for the New Year, and reflects the shape of the notation with the text (Lovely, good, wise, and pleasant). The graphic layout of the notation is a play on words on the "Cor" ("heart") in "Cordier".