chromaticism returns and the rhythms, enlivened by semiquavers, become unsettling for the listener. The alto resumes the fugue subject followed by a stretto entry of the soprano in its higher register five beats later. The bass then takes up a dance-like accompaniment in time, just before a stretto entry from the tenor. The bass continues for 6 bars of time (i.e. normal bars) introducing a short new motif involving a downwards drop of a fifth, linked to the fugue subject and already hinted at in the first section. The soprano plays the new motif in canon with the bass, until the bass resumes the subject, starting on the second beat of the bar, and the rhythm stabilises. The upper parts play a combination of the countersubject and the new motif and continue with them as an episode after the fugue subject ends. A further subject entry in the bass is followed by another episode based on the new motif as all the parts descend with chromaticisms to a cadence. Section 4 (bars 57–67). In the final section Bach is at his most inventive, creating what Kerman calls "sublime clockwork". The tenor part plays the fugue subject in augmentation like a cantus firmus in minims until the final pedal point F held for five bars. At the same time Bach adds one statement of the fugue subject in crotchets in the alto part, as a sort of "simultaneous stretto". Over this in the soprano he superimposes the second subject in quavers, that has not been heard since the end of the second section. There is a resumption of the clarity and harmoniousness last heard there as the alto and bass parts join the soprano polyphonically in the countersubject, continuing to the close over the pedal point. Four duets BWV 802–805 The descriptions of the duets are based on the detailed analysis in and . To listen to a MIDI recording, please click on the link. The four duetti BWV 802–805, in the successive tonalities of E minor, F major, G major and A minor, were included at a fairly late stage in 1739 in the engraved plates for Clavier-Übung III. Their purpose has remained a source of debate. Like the beginning prelude and fugue BWV 552 they are not explicitly mentioned on the title page and there is no explicit indication that they were intended for organ. However, as several commentators