Definition of "sirvente"

The knight in the meantime, had brought the strings into some order, and after a short prelude, asked his host whether he would choose a sirvente in the language of oc, or a lai in the language of oui, or a virelai, or a ballad in the vulgar English.

1819 December 20 (indicated as 1820), Walter Scott, chapter XVII, in Ivanhoe; a Romance. […], volume II, Edinburgh: […] Archibald Constable and Co.; London: Hurst, Robinson, and Co. […], page 42

[T]here was a little, sleek, fat clerk of the name of Chaucer, who was so apt at rondel, sirvente, or tonson, that no man dare give back a foot from the walls, lest he find it all set down in his rhymes and sung by every underling and varlet in the camp.

1891, A[rthur] Conan Doyle, The White Company, New York, N.Y., Boston, Mass.: Thomas Y[oung] Crowell & Company […], page 138