An filius non est Dei (Is He not truly God’s own Son?) is a Passiontide cantata if you trace the text Buxtehude used back to its origins you’ll find it comes from the Medieval hymn Salve mundi salutare – also known as the Rhythmica oratio, which is the Passiontide poem that Buxtehude used in his cantata cycle Membra Jesu nostri, BuxWV 75. There’s another link to that cantata cycle in the way that Buxtehude evokes the Passiontide atmosphere using strings (three violas da gamba and continuo). His poignant use of harmonies and the sharp key of B minor denote the pain of the Crucifixion while the sighing figures of the vocal strophes and the tremolos that end each ritornello add to mood of pious melancholy.
Text &Translation: An filius non est Dei
An filius non est Dei,
Is He not truly God’s own Son?
Quin immo Jesus est meus,
Jesus is mine for evermore.
Salveto, fons purissime,
Hail, gracious fountain bright,
O rima nobilissima,
Oh wound of high nobility,
Tu nectar es verissimum,
True nectar, healer, good and kind,
Longe sapor dulcissime,
Sweet perfume, sent to us from heaven,
Derived from Rhythmica oratio attributed