Cantata No. 50: the shortest of them all.

There's a cantata for that makes a pretty good tagline, or even philosophy of life.  Only have four minutes with a double chorus and orchestra?  Bach has you covered.  

No. 50 is that one oddball work which probably comes from a larger fragment, but might also be a random piece of another composer (gasp!).  The text is Luther's translation of Revelation 12:10:

Now is the salvation and the power and the kingdom and the might of our God and of His Christ come, since he is cast down who accused them day and night before God.

Revelation 12:7-12 is the epistle reading for St. Michael's, so it's possible that Bach could have composed this for a special festival performance, and the other movements got "misplaced."  Or - maybe it's a MOTET portion!  Theorizing is fun.  

If any other arrangement of the text was used, the attributes of Christ's glory would not have as much "punch" as they do.  Each thing ("Heil," "Kraft," "Reich" and "Macht") falls on a higher degree of the major scale - the upper neighbor, the third, fifth, and then octave in the sunny, triumphant key of D Major.

 The second subject, "Since he is cast down," descends in a laughing motion while each vocal part restates itself.  Once everybody is in, the trumpet, timpani, and rest of the instrumentalists jump into the victory party.  Right before the end, the second phrase is quietly repeated in a downward stepping motion, followed by a highly uncharacteristic chromatic slide and quick cadence.  

On a side note, this makes for mightily effective alarm-clock music. It's also quite helpful when I'm out running and encounter a particularly steep hill.  :)  Enjoy!

http://emmanuelmusic.org/notes_translations/translations_cantata/t_bwv050.htm#pab1_7
http://erato.uvt.nl/files/imglnks/usimg/6/6d/IMSLP01185-BWV0050.pdf
http://www.youtube.com/watch?v=AC_2_y2n0qc