This eight-voice motet may have been composed to provide choral exercises for his students. The motet's biblical text would have been suited to that purpose. The final four-part fugue is titled "Alles was Odem hat" ("All that have voice, praise the Lord!").
Robert Marshall writes that it is "certain" that this motet was one heard by Wolfgang Amadeus Mozart when he visited Leipzig's Thomasschule in 1789. Johann Friedrich Rochlitz, who graduated from the Thomasschule and remained in Leipzig to study theology in 1789, reported ten years later that Johann Friedrich Doles (a student of Bach, who through 1789 was cantor of the Thomasschule and director of the Thomanerchor) "surprised Mozart with a performance of the double-choir motet Singet dem Herrn ein neues Lied by Sebastian Bach... he was told that the school possessed a complete collection of his motets and preserved them as a sort of sacred relic. 'That's the spirit! That's fine!' [Mozart] cried. 'Let's see them!' There was, however, no score... so he had the parts given to him, and ... sat himself down with the parts all around him." Rochlitz also reports that Mozart requested a copy, and "valued it very highly..." 
^BWV2a: Alfred Dürr, Yoshitake Kobayashi (eds.), Kirsten Beißwenger. Bach Werke Verzeichnis: Kleine Ausgabe, nach der von Wolfgang Schmieder vorgelegten 2. Ausgabe. Preface in English and German. Wiesbaden: Breitkopf & Härtel, 1998. ISBN 978-3765102493, p. 228
^Rochlitz, Johann Friedrich, in the Allgemeine Muiskalische Zeitung, 1799, p. 117, translation from Robert C. Marshall, "Bach and Mozart's Artistic Maturity," pp. 69-17, in Bach Perspectives 3: Creative Response to the Music of J. S. Bach from Mozart to Hindemith, edited Michael Marissen, University of Nebraska Press, 1998, ISBN 0-8032-1048-5