One of the greatest of the so-called "chorale cantatas" that dominate Bach's second annual cycle of Leipzig cantatas, BWV 78 ("Jesus, Thou of my soul"), was composed for the 14th Sunday after Trinity in 1724, and first performed on September 10 of that year. The anonymous librettist based his text on the Johann Rist hymn (1641) from which the cantata takes its name. Deeply penitential in nature, the text bears little relationship to the appointed Gospel of the day (Luke 17:11-19), the story of the healing of the ten lepers. The scoring is for horn, flute, two oboes, strings, and continuo in addition to four-part chorus and soloists.
The cantata opens with a choral passacaglia that unfolds with majestic spaciousness over a descending chromatic bass line; Bach often used this device to illustrate sin -- or, in the words of the chorus, "grievous spiritual woe." The chorale melody is heard in the soprano line, which is supported by the horn and flute; only in the central section is the darkly expressive mood alleviated. The succeeding duet for soprano and alto is a wonderful example of Bach's word painting; the canonic vocal writing and forward-pressing continuo accompaniment provide a vivid illustration of hastening "with feeble but eager steps." The following recitative for tenor is long and dramatic, and the acute anguish of the text is sustained throughout; at times the recitative gives way to arioso. With the following tenor aria, the mood of the cantata starts to change, and the text begins to focus on the cleansing properties of Christ's blood. The final solo numbers, a recitative and aria for bass, take up this theme of redemption; the aria is a virtuosic movement that includes a demanding obbligato part for solo oboe. The final stanza of Rist's hymn forms the text of the concluding chorale, the hymn melody now treated to a simple, but moving four-part harmonization.