Filament opens its seventh season with a return to the music of J.S. Bach, this time giving pride of place to his Trio Sonatas for organ, transcribed by the ensemble for violin, treble viol, and keyboard. Each of these trio sonatas, originally written to help Bach’s son Wilhelm Friedemann perfect his keyboard technique, sparkle with brilliant dialogue. With this unusual, custom-fitted combination of instruments and its characteristic flair for reinvention, Filament will coax out all the polyphonic riches and prismatic color of these mature works.