The choral "O Herr Gott, Vater in Ewigkeit" is a choral meant for Trinity Sunday. Bach writes a piece in three parts, to emphasize the Trinitarian nature of God. The first part is titles "O Herr Gott, Vater in Ewigkeit", the second one "Christ" and the third "O Gott heiliger Geist". A similar ordening is to be found in J.S. Bach's Klavierübung, Part three. BWV 669-671 and BWV 672-674 each have succesively Gott, Christ and the Holy spirit as subject. In my youth I learned to play BWV 669-671 as firm, mild and strong respectively, as an expression of three of the aspects of God. Though this piece by J.M. Bach is on a much smaller scale as those three grand works of J.S. Bach, the Lutheranian believe is the same here, so I play them as I once learned how to play BWV 669-71.
In this work Neumeister shows himself once again to be a not so good scribe. The first part of this piece is in four parts, but in lots of places one of the parts just disappears. I firmly believe Johann Michael Bach was an excellent composer, and he would not write a four part piece so sloppy. So, I add some notes here and there, to maintain the four part character of the piece.
Score availalbe here: http://partitura.org/index.php/johann-michael-bach-o-herr-gott-vater-in-ewigkeit