Mass in B Minor, BWV 232

When Johann Sebastian Bach set himself to work on a new composition, it was normally just a matter of days, at most a week or two, before it was finished. Such was certainly not the case with his Mass in B Minor, BWV 232. The fourth part (Sanctus) dates from 1724; the first two parts (Kyrie and Gloria) were completed in 1733; the third part (Credo), as well as the work’s final autograph score, date from 1748, just two years before the master’s death. Bach’s B Minor Mass will be performed by the Milwaukee Symphony Orchestra and Chorus tonight and tomorrow night at 8 p.m. at the Marcus Center.