Northfield, the locally-based 10-member a cappella vocal ensemble, that has been a regular part of seasonal celebrations in Western Maine for more than 25 years, and will present two performances this month filled with music. Concerts are planned for 7 p.m., Saturday, Dec. 19, at the Rangeley Congregational Church, and at 3 p.m., Sunday, Dec. 20, at  St. Luke’s Episcopal Church in Wilton. The singers will share their love of songs of the season in French, German, Spanish, Italian, Hebrew, Yiddish, Latin and English. A special group of arrangements of “In Dulci Jubilo” will be performed: the first arranged for two vocal parts, then four, then two verses filled out with eight voices. The program will also include varying styles and sounds; music by Byrd, Josquin des Prez, Salamone Rossi, several in the Early American Shape Note tradition, as well as light-hearted modern adaptations supplied by P.D.Q. Bach and Garrison Keillor. Donations will be accepted at the door for all performances