Created in 2011 by artist director Jeannette Sorrell and Montreal-based lutenist Sylvain Bergeron, Sacrum Mysterium: Sacred Mystery, A Celtic Christmas is one of Apollo’s Fire’s most popular programs. The show includes “excerpts from the 13th-century Vespers of St. Kentigern (patron saint of Glasgow, Scotland) with ancient pagan carols, renaissance choral music, traditional Celtic fiddle tunes and joyous dances.” The Cleveland-based baroque orchestra will perform the piece today at 4 p.m. at the Masonic Auditorium. Families should consider attending the earlier family concert that takes place at 1 p.m. Tickets range from $10 to $50 for the family concert and from $22 to $68 for the later show. (Niesel)