Cantata no. 128: Auf Christi Himmelfahrt allein, BWV.128

Auf Christi Himmelfahrt allein (On Christ's ascension into heaven alone), BWV 128, is a church cantata by Johann Sebastian Bach. Bach composed it in Leipzig for the Feast of the Ascension and led the first performance on 10 May 1725.

It is the fourth of nine cantatas on texts by Christiana Mariana von Ziegler, with whom Bach collaborated at the end of his second cantata cycle. It begins, unlike the previous three, with a chorale fantasia like the chorale cantatas, using the first stanza of a 1636 hymn for Ascension Day by Ernst Sonnemann. For a closing chorale she used the fourth stanza of "O Jesu, meine Lust" with text by Matthäus Avenarius. The theme of the cantata is the reaction of the believer to the absence of Jesus, including hope to see him again "face to face". Bach scored the cantata for three vocal soloists (alto, tenor and bass), a four-part choir and a Baroque instrumental ensemble of two horns, trumpet, two oboes, oboe d'amore, oboe da caccia, strings and basso continuo, in a rich and varied instrumentation.