Composed for the Second Day of Christmas, which fell on December 26, 1724, Bach's Cantata No. 121 "Christum wir sollen loben schon" (Christ, we shall well praise) (BWV 121) sets a pair of chorales by Martin Luther flanking four movements setting texts by an unknown poet based on Luther's chorales. The cantata is scored for tenor, alto, bass and soprano soloists, chorus, oboe d'amore, strings, and basso continuo with a coronet and a trio of trombones in the outer movements. The opening and closing movements of "Christum wir sollen loben schon" start in E minor, but close a whole tone higher in F sharp minor, a harmonic pattern that is so unusual as to be almost unique in Bach's cantatas. The pattern of starting a movement in one tonality and ending in another is carried through in the second, third, and fifth movements. The second movement starts in B minor then modulates to G major for the central section; the third begins in F sharp minor and ends in C major, the tonality of the fourth movement; and the fifth starts in F sharp minor and ends in B minor. The first movement is a powerful choral fugue on an archaic subject, with the full orchestra doubling the chorus throughout. The second movement is an austere da capo aria in the form of a trio sonata for tenor soloist, oboe d'amore, and continuo. The third is a severe secco recitative for alto soloists and organ continuo and the fourth is a robust aria for bass soloist accompanied by strings and continuo. The fifth is a second secco recitative for fervent soprano soloist and continuo. "Christum wir sollen loben schon" concludes with a strong-boned harmonization of the second Luther chorale for chorus and orchestra colla parte. ~ James Leonard, All Music Guide
