If you go

What: “A Baroque Christmas”

When: 7:30 p.m. Saturday, 2 p.m. Sunday

Where: Tower Theatre, 835 N.W. Wall St., Bend

Cost: $18, plus fees, available through the venue

Contact: www.tower theatre.org or 541-317-0700

This weekend, the voices of Central Oregon Mastersingers will once again fill the Tower Theatre with the sounds of Christmas.

It’s the third year the Mastersingers will perform at the Bend theater (see “If you go”). Plan accordingly: Mastersingers’ concerts in 2011 and 2012 sold out, and this weekend’s performances are selling well, said the group’s director, Clyde Thompson, adding that there are no plans to add a third performance.

The seats on stage will be similarly full. The concert features some 70 musicians and singers performing carols and familiar holiday tunes, among them Thompson’s adaptation of Boston Symphony’s arrangement of “The Twelve Days of Christmas,”

The main part of the concert is devoted to Johann Sebastian Bach’s “Magnificat,” “a cornerstone in the repertoire for choir,” Thompson said.

“Magnificat” is Bach’s famous musical setting of the liturgical text Magnificat anima mea Dominum, or “My soul doth magnify the Lord,” in which “Mary expresses her joy and thanksgiving at having been chosen to conceive God’s son,” Thompson writes in the program notes.

Bach wrote it in 1723, after taking a job directing music for the Lutheran churches of Leipzig, Germany.

At the time, “He was 38 years old, and he was actually not all that popular a composer in his own time,” Thompson explained. “He’s the one that pretty much sums up everything that had happened in Western music up to that point, pulled it all together and brought it to a new level.”

As a result, however, people in Bach’s time viewed his music “as a bit old-fashioned and just a little bit too heavy and thick.”

In other words, Bach may have had something to prove.

“It may be that when he started the job he was very motivated to prove himself,” said Thompson. “The most extraordinary creative period in his life was those next two years.”

Bach would remain on the job for 27 years, but in those first two years he wrote about 120 cantatas.

The baroque cantata was a multi-movement work written for singers accompanied by instruments, Thompson explained. “(It’s) safe to say that it was an important form of vocal music during the baroque period, especially because of Bach’s output.”

Bach also wrote a handful of secular cantatas, but he was very focused on church cantatas, which “served as weekly musical sermons,” Thompson said.

“That’s more than one cantata a week, which is just phenomenal,” he said. “He wrote a cantata for every Sunday and every special feast day.”

In 1733, Bach revised “Magnificat” from its original form — E-flat major — a half-step to the key of D, “which is a more brilliant, kind of a celebratory key,” Thompson said. “That’s the one that’s mostly done now, and the one we’re doing. It’s just a brilliant piece.”

There will be 10 featured soloists in the concert, and “Magnificat” features five of them — Trish Sewell, Katy Hays, Melissa Carter, Christian Clark and Danny Brown. A 24-piece orchestra will join the Mastersingers for “Magnificat” as well as two other pieces on the concert program.

The program also features Mannheim Steamroller’s arrangement of “Deck the Halls,” with Scott Michaelsen and Ben Larson as soloists on keyboards.

Michaelsen, who did musical direction for “Spamalot” this fall, also wrote an arrangement of “We Three Kings” that Thompson included on the program.

— Reporter: 541-383-0349, djasper@bendbulletin.com