THE FOLGER Theatre has concocted a Medieval Christmas Pageant of three dramatic pieces that are normally encountered only in a theater history course. The play is preceded by a local version of a medieval marketplace in the Great Hall, starting a half hour before show time.

Each is an example of a type of theater peculiar to its time, although one of the pieces, "The Shepherds," is said to be the precursor of opera. It is called a liturgical drama, with origins in the huge churches of 13th-century France. By putting a biblical story to music, the clergy hoped to make services a bit more lively around the Christmas season; young people generally were the performers.

The version the Folger is using was transcribed from photographs of the original manuscript in the cathedral at Rouen by Prof. Fletcher Collins, theater professor emeritus of Mary Baldwin College, whose passion is the intersection of words and music. "The biggest problem," he said of the transcribing work, "is that the music notation includes no meter. We have determined the meter from the (Latin) verse, which some will argue about."

The original Latin of the play has been retained, said director Ross Allen, and the Folger Consort will play stringed instruments, recorders and various other historically correct items. In keeping with custom of the time, female parts will be played by male countertenors (except for one female angel).

"The way we'll get the feel of it is with stylized movement," said Allen, "which we know about only from studying the art of the time. To be honest, a lot of it is guessed."

This play is the centerpiece of the pageant, although it lasts only about 11 minutes.

"You have to take it on its own terms," he added. "Time and space stand still, and you must surrender."

As the centuries went on, the liturgical dramas were moved outside the church; in England labor guilds took over the performances. Nonreligious elements began to creep in, although the themes were still biblical. The stories were performed on wagons during the Corpus Christi celebration in August, which lasted for days, and each group specialized in a separate chapter of Christ's life, up through the Resurrection.

"The Second Shepherd's Play" is one of these, part of what is known as the Wakefield Cycle, which comprises 32 plays. In both style and content it is more rambunctious than its predecessor.

The story has a biblical ending, but before that the script sounds almost like one for the Three Stooges.

It begins with three shepherds chatting. One moans about how the shepherds of the world are put upon, another complains about his love life, and a third goofs off. A devil figure called Mak, known as a thief, puts a spell on them and steals their sheep. In an effort to hide the stolen lamb, he pretends it is a baby and puts it in a crib. The shepherds, noticing among other signs that the "baby" does not smell like one, catch onto the ruse, but then an angel appears and tells them to get to Bethlehem. The rest of the story is familiar.

Allen scoured two dozen translations from the Old English before settling on one by Englishman Martial Rose, which he chose because it was easiest to understand. Example:

"Lord the winds are spiteful/the storms so keen/and the frost so sharp/they water mine een," in one translation, became "Lord this weather works through us/ the wind is so keen/ the frost will undo us/half blind I have been."

In a more graphic illustration, one version had a character saying "mend your lip," while Rose translated the same passage as "take out that Southern tooth and put in a turd."

"It's a mixture of the grotesque and the vulgar that was so much a part of medieval life," said Allen.

The curtain-raiser is called "The Mayor's Christmas Pie," and it is derived from a type of play called the rogue, or beggar's play. The theme always has to do with common men getting the better of rich people. "It was a proletariat play, popular street theater," said Allen. "The language is the vernacular of the day." In this case, two beggars trick a fat and pompous baker out of a Christmas pie and tart.