Turning a concert into a seasonal event is easy in December just tack on the words "Christmas concert" and anything with Latin in it becomes a fitting -celebration of the season. The number of holiday-related related musical events around campus in the coming week--ranging from the do-it-yourself to the formally prepared--is so high that carolers and chorus lovers will have to work hard to avoid potential traffic jams.

"Masses are good for all times and places," says Beverly Taylor, associate director of choral activities, whose two choral groups, the Radcliffe Choral Society (RCS) and the Harvard Radcliffe Chorus are both preparing bona fide Christmas concerts for the coming week The Bach Magnificat in D has come to be a Mass that is especially good for Christmas, and the RCS will perform it next Monday with its traditional male counterpart, the Harvard Glee Club.

The rest of the program, which the two groups traditionally split, ranges from arrangements of carols by the Glee Club to sacred-sounding set pieces. With the move to Sanders from St. Paul's Church, where last year's concert was held, the groups have eliminated the audience-participation carols which used to splice pieces together in the concerts. "That was just to cover our walking from place to place," explains Taylor.

A more carol-heavy experience is available at Memorial Church, also on Monday night (and repeated Tuesday afternoon and evenings). The University Chou a low profile mixed singing group will alternate Scriptural readings and sing along carols in a turn-of-the-century English format called "lessons and carols." On Tuesday night, the performance will come on the heels of a some what less structured holiday performance outside in the Yard featuring the mixed Harvard Radcliffe Chorus, strolling in circles and sending up Christmas carols to the freshman dorms (The Chorus formal holiday concert came this past Sunday, to beat the Christmas rush).

The opportunity to draw festive campus crowds lures outside musicians to Harvard as well. The Pro Arte Chamber Orchestra a small professional group known for its stints in the Boston area, will play in Sanders December 12. The program also draws on the ever-useful Mass--one of Bach's (in G) and one of Stravinsky's.

A week later, a three year-old local group called Spectrum Singers will hit a bit closer to the mark with William Byrd's "Hodie Christus Natus Est." (If you can't translate this one, anyone you hear practicing scales can probably help you out) Along with pieces by Bach and Mendelssohn, the Spectrum will also throw in a beautiful and often-performed Randall Thompson work called "Alleluia" (No translation problems here: The lyrics consist of one repeated word, and here's a hint--it's somewhere in the title.)

Religious imbalance of the season may be less noticeable than usual this year. As it happens, about 365 Christmas or "sacred" pieces of music have been written for each concert work with a Hannukah theme Nevertheless, at least one such piece exists, and the Collegium Musicuum is slated to perform it in Sanders on December 12.

Handel's oratorio Judas Maccabeus chronicles the rise of the revolutionaries to save the Hebrews from Greek and Syrian interlopers in post-Biblical times, it's also a momentous enough piece to knock a chorus and audience out for the rest of the night, what with trumpets bells, and victory chants.

The Collegium is sponsored in the endeavor by the parents of Karen Avra Gordon '84, who died last year and was a member of Hillel. Her father (Professor of Chemistry Roy Gordon) and mother mean to sponsor a religious or Israeli musical event each term for the next several years.

And what of those who want to act out a bit of their celebration, whichever it may be? Caroling is a popular alternative, especially when the snow is falling properly to create ambience, and at least one freshman entryway plans to go walking and warbling as a group this season. The close-harmony Radcliffe Pitches have been known to do the same.

Larger-scale audience-participation comes with another seasonal anomaly--the proliferation of "Sing-Ins," in which audiences buy or bring scores to a performance and sight-read the chorus under the direction of host-provided conductors. The most unusual such event this may come at Currier House on Sunday, as concert-planners hope to include a sight-singing of Benjamin Britten's Ceremony of Carols in a performance by the Currier Singers.

Dunster and Mather Houses, coming out for tradition, will host their annual sing-in December 15, presenting the single piece most consistently associated with the Christmas season: Handel's Messiah. It's often forgotten that this glorious oratorio was composed at an entirely unseasonal time of year, and traces the whole life of Christ, not just the Nativity. But who cares--all those baroque flourishes suggest nothing if not Christmas trees, and the chorus praising, "God, who doth make Intercession for us" is as mercifully timely as ever. A Week of Music Back Society Orchestra:  Sanders Theatre  Saturday 12/11, 8:30 (Chamber Music 8:00) Pro Arte Chamber Orchestra:  Sanders Theater  Sunday 12/12, 7.30 Collegium Musicuum: Judas Maccabeus  Sanders Theater  Sunday 12/12, 7:30 Currier Singers:  Currier Fishbowl  Sunday 12/12, 8:00 Harvard Glee Club-Radcliffe Choral Society  Sanders Theater  Monday 12/13, 8:15 University Choir:  Memorial Church  Monday 12/13, 8:30 "Lessons and Carols"    Tuesday 13/14, 2:30, 8:30 Messiah Sing-In  Dunster Dining Hall  Wednesday 12/15, 8:00 Spectrum Singers  Paine Hall  Sunday 12/19, 3:00