Kalenda Maya by Raimbaut de Vaqeiras (Fl. 1180 - 1207)

This is a troubadour song (secular) written by Raimbaut which features what we call the refrain form.  In the version I am listening to right now it begins with just the instruments (fiddle, flute, drums, and some kind of guitar) and then a male soloist sings the lyrics listed below.  I actually found a pretty good translation of the song on this website:  http://www.trobar.org
The melody that is used was probably borrowed from a purely instrumental tune of his time.  It is a simple tune, but one that gets stuck in your head, especially because of how often it repeats the same melody.  It is one of the oldest songs of its type to survive to the present.  

Kalenda maia Ni fueills de faia Ni chans d'auzell ni flors de glaia Non es qe.m plaia, Pros dona gaia, Tro q'un isnell messagier aia Del vostre bell cors, qi.m retraia Plazer novell q'amors m'atraia E jaia, E.m traia Vas vos, donna veraia, E chaia De plaia .l gelos, anz qe.m n'estraia.	Neither calends of May, nor leaves of beech nor songs of bird, nor gladiolus flowers are of my liking, o noble and merry lady, until I have a fleet messenger of your beautiful person to tell me of new pleasures love and joy are bringing; and I repair to you, true lady; and let me crush and strike the jealous, before I depart from here.
Ma bell' amia, Per Dieu non sia Qe ja.l gelos de mon dan ria, Qe car vendria Sa gelozia, Si aitals dos amantz partia; Q'ieu ja joios mais non seria, Ni jois ses vos pro no.m tenria; Tal via Faria Q'oms ja mais no.m veiria; Cell dia Morria, Donna pros, q'ie.us perdria.	My beautiful friend by God, this never be: that out of jealousy one scoffs at my harm, he'd command a dear price for his jealousy if it were such as to part two lovers; Since never again I'd be happy nor would I know happiness, without you; I'd take such a way that I'd never be seen by men again; that day I'll die, brave lady, in which I lose you.
Con er perduda Ni m'er renduda Donna, s'enanz non l'ai aguda Qe drutz ni druda Non es per cuda; Mas qant amantz en drut si muda, L'onors es granz qe.l n'es creguda, E.l bels semblanz fai far tal bruda; Qe nuda Tenguda No.us ai, ni d'als vencuda; Volguda, Cresuda Vos ai, ses autr'ajuda.	How could I lose or retrieve a lady, before I have had her? neither leman nor lover is such by imagination alone; but when a suitor turns into a lover great is the honour he has accrued, such is the fame produced by a sweet glance; yet naked held you I have never, nor others have won you; longed for, obeyed you I have, without any meed.
Tart m'esjauzira, Pos ja.m partira, Bells Cavalhiers, de vos ab ira, Q'ailhors no.s vira Mos cors, ni.m tira Mos deziriers, q'als non dezira; Q'a lauzengiers sai q'abellira, Donna, q'estiers non lur garira: Tals vira, Sentira Mos danz, qi.lls vos grazira, Qe.us mira, Cossira Cuidanz, don cors sospira.	I'd hardly rejoice should I part from you, my Beautiful Knight, in sorrow, since it doesn't turn anywhere else my hart, nor drags me my desire, since it desires naught else. The slanderers, I know, would be pleased, lady, as otherwise they'd find no peace. Such one would see and listen to my loss, who would be indebted to you for it as he looks at you and considers in his presumption, for which my heart sighs.
Tant gent comensa, Part totas gensa, Na Beatritz, e pren creissensa Vostra valensa; Per ma credensa, De pretz garnitz vostra tenensa E de bels ditz, senes failhensa; De faitz grazitz tenetz semensa; Siensa, Sufrensa Avetz e coneissensa; Valensa Ses tensa Vistetz ab benvolensa.	So kindly blossoms, shining above all, noble Beatriz, and so kindly grows your valour; in my opinion your dominion is adorned with worth and of fair speech, without doubt. You are the source of gracious deeds; learning and mercy you have, along with knowledge; valour beyond all dispute you clothe in kindness.
Donna grazida, Qecs lauz' e crida Vostra valor q'es abellida, E qi.us oblida, Pauc li val vida, Per q'ie.us azor, donn' eissernida; Qar per gencor vos ai chauzida E per meilhor, de prez complida, Blandida, Servida Genses q'Erecs Enida. Bastida, Finida, N'Engles, ai l'estampida.	Gracious lady, everyone praises and proclaims your worth, which gives such pleasure; and he who forgets you, prizes life but a trifle and so I adore you, distinguished lady; since I have chosen you as the kindest and as the best, laden with worth, I have flattered and served you more kindly than Eric did Enid. Composed, and ended, Dame Engles, I have the estampida.