Across the Charles River in Cambridge, a decades-long tradition continues at Harvard’s Sanders Theatre December 9–27. Christmas Revels, the 46th annual showcase of singing and dancing that marks the winter solstice, has annually highlighted the rituals of cultures both near and far, from Appalachia and Victorian England to Russia and Spain. This year features the folk traditions of Acadian immigrants, who were forced by the British southward from Canada and Maine to Louisiana, establishing that region’s colorful Cajun society. Familiar Revels touchstones remain, however, including the first act finale “Lord of the Dance” number, a mix of old English song and dance that literally sweeps the audience away into the lobby for a moment of joyous communal celebration.