Dame Fortune can wake the world to laughter and mirth, but by night can also steep a few hard-luck souls in the blackest of blues. For their performance this weekend at Mount Vernon College, members of the Musica Antiqua early music chamber ensemble have pored over everything from medieval paintings to 19th-century catalogues of medieval and Renaissance music, researching the plethora of period tunes inspired by the ancient Lady Luck.

"She's fickle and capricious," says John Guillory, director of the group. "She's prone to reward one moment and dash all hopes the next."

Musica Antiqua, formed in the early '70s, is an eclectic group of daytime lawyers, technical editors and scientists and several full-time musicians and musicologists, who in their spare time dig up forgotten music and resurrect it on their beloved period instruments. As Guillory suggests, only when played on these ancient instruments do the music's themes and tonal colors come back to life.

What they found in Jacob Obrecht's "Fortuna Desperada" and many other songs from the 13th through 16th centuries wasn't so surprising considering the time. "Things were less complacent. The unpredictable was more central to people's thinking," says Guillory.

Performances will be at 8:30 p.m. on Saturday and 4 p.m. next Sunday in Post Hall at Mount Vernon College. For more information, call 726-1216.