The cantata begins with the instrumental Sinfonia.
Set in G major, it is in a triple meter in siciliano rhythm.
Albert Schweitzer likened the music to a concerto of the shepherds, playing oboes, and the angels playing strings and flute in unison with the first violin.
The movement is a ternary form, ABA', repeating the beginning modified after a middle section, and this a forerunner of the classical sonata form, as Dürr notes.
Each section is in again three groups, taking the analogy to the sonata form further: string music, as a first theme, is followed by oboe music as a second theme and combined music as the closing group.
The movement is the only purely instrumental music in the Christmas Oratorio.

The absence of a chorus in the first movement signifies the stillness of the nightly scene, giving more weight to the voices to follow.
The major choral movement in this cantata is the representation of the angels' song.
The cantata begins with the instrumental Sinfonia. Set in G major, it is in a triple meter in siciliano rhythm. Albert Schweitzer likened the music to a concerto of the shepherds, playing oboes, and the angels playing strings and flute in unison with the first violin. The movement is a ternary form, ABA', repeating the beginning modified after a middle section, and this a forerunner of the classical sonata form, as Dürr notes. Each section is in again three groups, taking the analogy to the sonata form further: string music, as a first theme, is followed by oboe music as a second theme and combined music as the closing group. The movement is the only purely instrumental music in the Christmas Oratorio.
The absence of a chorus in the first movement signifies the stillness of the nightly scene, giving more weight to the voices to follow. The major choral movement in this cantata is the representation of the angels' song.
Und es waren Hirten in derselben Gegend, BWV 248 II