By Raimbaut de Vaqueiras. The razo (a prose introduction that was often attached at the start of troubadour songs, often giving biographical details - real or fictional) give the story of the origin.

"You have certainly heard who Raimbaut was and where he came from and how he was knighted by the Marquis of Montferrat and how he paid court to Lady Beatrice and on account of his love lived joyously.
And hear how he experienced during a short time great sadness. This was caused by the false jealous ones who found love and courting displeasing. They spoke to Lady Beatrice in the presence of the other ladies saying: "Who is this Raimbaut de Vaqueiras even though the Marquis made him a knight? And how dare he court so high born a lady as you are? Be it known that it is not an honor either for you or for the Marquis." They said so many evil things (as bad people do) that Lady Beatrice became angry at Raimbaut de Vaqueiras. So when Raimbaut tried to woo her and ask her pity, she did not listen to his prayers, but to the contrary told him that he should woo another lady who would be more appropriate for him and that she would no longer listen to him. And that is the sadness Raimbaut had during a short time just as I told you at the beginning of this razo.
So he stopped singing and laughing and withdrew from all activities that might please him. That was too bad. All this was caused by the tongues of gossips, just as he tells it in one stanza of the estampie you will hear.
At that time two jongleurs came from France to the court of the marquis who were skilled at playing the vielle. And one day they played an estampie that much pleased the marquis, the knights and the ladies. But Raimbaut did not enjoy it. The marquis noticed this and said to him: "Sir Raimbaut, why do you not sing and rejoice since you are listening to a fine sound of the vielle, you see here so beautiful a lady as my sister who has retained you as her servant, and she is the noblest lady in the world?" And Raimbaut replied that he would do nothing. Now the marquis knew why, and he said to his sister: "Lady Beatrice, for the love of me and of all these people, I want you to agree to beg Raimbaut, in the name of your love and your grace, that he be happy, that he sing, and that he enjoy himself, like he
used to." And Lady Beatrice was so courtly and of such good grace that she begged Raimbaut, encouraging him, for her sake, to be happy again and to again make a song.
So Raimbaut, for the reason you've just heard, made the estampida that runs like this:

(from Rosenberg, Switten, leVot: Songs of the Troubadours and Trouveres.)

They say that despite the razo calling it an estampida (estampie) it is not in that form, possibly explained by the tune coming from the heard instrumental of the razo.Also, it could be argued that the tune for Kalenda Maia might be the only surviving pre-13th century piece of instrumental music.

The text appears in several manuscripts, the tune in only one. You can see the melody in the Troubadour melodies database: Kalenda Maia. (Some info on the encoding there can be found here:
Encoding Song in the Troubadour Melodies Database

There is some freedom in the interpretation of the tunes (only some 260 or so have known melodies) are most have only a simple melody recorded and the rhythm is open to interpretation. (There was some rhythm but either performers knew what it was (conventionally) or the scribes were unable to note it down).


Mick