(O pleasing melody), BWV 210a', is a secular cantata by Johann Sebastian Bach. Featuring a solo soprano, it was perhaps the longest of Bach's solo cantatas. He wrote it in Leipzig as a "Huldigungskantate" (homage cantata) for Christian, Duke of Saxe-Weissenfels. First performed on 12 January 1729, the cantata became part of his repertory of congratulatory and homage cantatas, dedicated at least twice to different people and occasions. Bach used it as the base for his wedding cantata . Most of the music of was lost, but can be reconstructed from the later work, which survived completely.