The scene is outside a medieval castle, shortly before dawn. The lord is away from home on business -- bashing heads, most likely -- and during his absence a friendly troubadour is keeping the lady company. Outside, a friend of the troubadour's is watching for intruders and singing a song of warning about the approach of dawn.

This is the "alba" or dawn-song -- a common theme of the medieval lyric, like the "pastorella," in which a troubadour out riding alone meets a young shepherdess and propositions her -- with results that vary from one song to the next.

Both were prominently featured -- along with satires, love songs, elaborate allegories and a funeral lament for King Richard the Lionhearted (who was also a troubadour) -- in "Troubadours and Jongleurs," the season's opening program by the Folger Consort, which will have its two final performances at the Foger Library at 5:30 and 8:30 today and will be broadcast at 11 p.m. next Saturday on WGMS.

From its opening alba, "Reis Glorios" by Giraut de Bornelh, to the final "Kalenda Maya," a courtly variation on a wild peasant dance, the program was intelligently chosen, meticulously prepared, sung and played with exquisite musicianship and a fine sense of the varied styles in one of music's more complicated periods.