When Bach started work on his Christmas Oratorio, in 1734, he was at the peak of his creative powers: he was kapellmeister of Saint Thomas’s in Leipzig and head of the city’s esteemed collegium musicum; the Saint Matthew Passion was behind him, the great B minor mass just ahead. In two years he wrote the sprawling oratorio’s six cantatas, taking his texts from the biblical story of the Nativity and much of the music from his own earlier work, especially the cantata Tönet, ihr Pauken! Erschallet, Trompeten! (“Resound, you timpani! Ring out, trumpets!”). In turn, each of the six consists of arias, duets, chorales, and orchestral interludes, their tone ranging from celebration to wonderment to pious contemplation. In the first, Jauchzet, frohlocket, auf, preiset die Tage (“Rejoice, exult, arise, praise the days”), trumpets and drums herald Joseph and Mary’s arrival in Jerusalem, and the pageantry continues as an evangelist proclaims the birth of Christ. If these aren’t among Bach’s greatest cantatas–he wrote well over 200, so it’s not an easy question to settle–they’re definitely in the running. In this weekend’s program, the Chicago Symphony Orchestra will perform the first three cantatas–all time would permit–in their entirety for the first time; it’s hard to believe it took them so long to get around to them. Under Georg Solti the CSO earned renown for its renditions of Bach’s choral works, and at this concert it will be led by German conductor Peter Schreier, one of the most eloquent lyric tenors in the world and an astute interpreter of Bach–he made his CSO debut two years ago with the Saint Matthew Passion. Schreier’s 1986 recording of the Christmas Oratorio with the Rundfunkchor Leipzig is a standout–the singing is delicate yet stirring, the phrasing meticulous, the orchestral playing sensitive to the nuances of the period–but the CSO’s performance could easily match it. Schreier will sing the role of the evangelist; the other soloists will be soprano Ute Selbig, baritone Egbert Junghanns, mezzo-soprano Rosemarie Lang, and tenor Thomas Cooley. Thursday (December 16) through Saturday, 8 PM, Orchestra Hall, Symphony Center, 220 S. Michigan; 312-294-3000 or 800-223-7114. Ted Shen