The cantata BWV 145 is an unusual pastiche. The opening chorale is undoubtedly a Bach harmonization but was probably added to the cantata by his successor at Leipzig after his death. The chorus is by Telemann. The duet and aria as well as the final chorale are authentic Bach but probably the two concerted pieces are from Cöthen models a decade earlier.
For all of its varied genesis, this is a unified and successful cantata. The beautiful chorale harmonization that begins the work has a quiet grace that is characteristic of Bach’s best mature Easter pieces. The Telemann chorus is one of his best and is very worthy of Bach’s company. It begins with a bouncy irresistible duet for the women; as the men’s voices enter, so does the orchestra bringing the chorus to a rousing conclusion. The duet for soprano and tenor with violin obbligato is very much in the style of Bach’s great Cöthen works. This was a period when Bach wrote little religious music. In his Leipzig years Bach would occasionally dip into his secular cantatas from his Cöthen era for material for his sacred works. This happy work shows not only an intricate relationship between the two vocal parts, but the incorporation of the brilliant violin part is unusually skillful. The bass aria is unusual in that it has independent parts for all of the treble instruments and no middle voices. The lively interplay between the flutes and oboes is charming and totally suited to the happy text. “Erschienen ist der herrlich Tag.” was one of the favorite Easter Chorales in Bach’s day and here receives a granite-like powerful harmonization.