As the prominent composer, music theorist and contemporary of Johann Sebastian Bach and George Frideric Handel, Johann Mattheson, states in one of his writings in 1739, composing two- and three-part pieces meant reaching the peak of mastery in their trade for the musicians of the late Baroque. The present trio sonatas and duets of Johann Sebastian Bach‘s eldest son Wilhelm Friedemann, who was the most talented composer of them all according to his father‘s opinion, belong to the outstanding chamber music works at the close of the Baroque era. What Mattheson expected of this musical genre is demonstrated here in the dense polyphonic interplay of the two fl ute parts in an exemplary manner: „the genre consists in a concertante character - set for example for two instruments and a bass - since, so to speak, the two upper voices take up with one another and play competitively“.