broken chords recalls the writing in the first movements of the sixth trio sonata for organ BWV 530 and the third Brandenburg Concerto BWV 1048. BWV 804 has the following musical structure: bars 1–4: subject in G major in right hand followed by response in D major in left hand bars 5–6: transition bars 7–10: subject in G major in left hand followed by response in D major in right hand bars 11–15: transition to E minor bars 16–19: subject in E minor in right hand followed by response in B minor in left hand bars 20–23: transition bars 24–25: subject in C major in right hand bars 26–27: transition bars 28–31: subject in G major right hand with canon at octave in left hand bars 32–33: transition bars 34–37: subject in right hand with stretto at octave in left hand after a quaver bars 38–39: subject in G major in right hand Duetto IV BWV 805 BWV 805 is a fugue in strict counterpoint in the key of A minor, 108 bars long. The 8 bar subject starts in minims with a second harmonic half in slow quavers. Bach introduced further "modern" elements in the semitone drops in the subject and later motifs (bars 4 and 18). Although all entries of the subject are either in A minor (tonic) or E minor (dominant), Bach adds chromaticism by flattening notes in the subject and sharpening notes during modulating passages. Despite being a rigorous composition with carefully devised invertible counterpoint, i.e. with parts that can be interchanged, in parts its style is similar to that of the bourée from the Overture in the French style, BWV 831 from Clavier-Übung II. There are three episodes which move between different keys and combine three new pairs of motifs, either 2 bars, 4 bars or 8 bars long, in highly original and constantly changing ways. The first episode starts in bar 18 below with the first pair of new motifs, the upper one characterised by an octave drop: At the end of the first episode, the second harmonious pair of motifs is introduced: The third pair of motifs, which allows significant modulation, appears for the first time in the second half of the second episode and is derived from the second half of the subject and countersubject: The musical structure of BWV 805 has been analysed as follows: bars 1–8: subject in left hand,