Yet another trio

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In the last post, I introduced altogether 4 trios by J. S. Bach: [1] a movement from Cantata 140 for tenor chorus, obbligato violin, and basso continuo (a keyboard instrument with the bass possibly reinforced with cello or double bass),  [2] another movement, from Cantata, 85 again for tenor, a melody for two violins and viola (I'm still not clear about the scoring of the original movement) and basso continuo, [3] a trio sonata, BWV 525 in E Flat for organ, to which I added [4] the Trio Sonata from the Musical Offering, for Flute, Violin, and basso continuo.

I had forgotten to include another favorite movement, one of the first that I actually owned: this one is the slow movement from the beautiful Triple Concerto in A minor for Flute, Violin and Harpsichord.  In the middle movement, only the soloists play, possibly with a cello doubling the bass line of the harpsichord.  I have heard the piece played with the cello and without, and it sounds fine either way, and we won't get into big arguments about which way is correct, because sufficiently many others have expended a lot of energy arguing both sides, without settling it one way or another.  My suspicion is that it was performed either way, depending on the acoustics of the venue, and how powerful the bass of the harpsichord might have been.  (By the way, the German term for harpsichord is Klavier or Clavier, and the French and Italian term was Clavecin, or Cembalo.)

Here is a passable performance on YouTube.

If you listen through this piece, and also the Musical Offering trio, you will notice something interesting.  Each part can be split into several recognizable sections, which are recycled over and over throughout the piece.  Furthermore, the sections in all three parts are often the same; in other words, Bach built the entire movement by assigning certain blocks of tunes to the three instruments, and rearranging them differently in vertical blocks.  This technique did mean that Bach had to do less writing on the whole, but obviously the melodies had to be adjusted to fit the harmony.  But also, it made sure that the three instruments each got to play every melodic theme (making obvious allowances for the special duties of the bass line).  Isn't that interesting?

Here are the first three pages of screen captures of the score, with the various themes color coded.  The chromatic Royal Theme is in purple.  (This is the slow theme that goes up in an arpeggion--a broken chord--then creeps down in semitones; very distinctive.)

I gave up that idea; instead, I annotated the video I had originally made of the Allegro of the Trio Sonata of the Musical Offering, to include graphics that highlight the themes.  I found it too difficult to do a good job of it, so some of the highlighting doesn't last as long as it must, and I failed to indicate the recapitulation of the main theme at the very end.  Still, this highlighting tool provided by YouTube itself is moderately handy for minor annotations, and I have probably horribly abused it.  Here it is again:


So, there you go.