Whether Bach ever envisaged such a concert presentation is highly unlikely, since this systematic, 75-minute cycle of fugues and canons is all constructed on one theme and all in the key of D minor. Nor did he leave any indications of instrumentation, though if a player can read the four-stave "open score", most of it lies within the grasp of one pair of hands.
Koopman's contention that dividing the parts between four hands clarified the texture did not always work out. This was partly because both players tended to decorate their parts elaborately, which amplified the fizz of overtones that harpsichords tend to produce.
Matters were not always helped by a tendency, once a fugue was launched, to push the pace. Some eloquent and exciting things were heard, nonetheless. The pair of fugues constituting Contrapunctus XIII were hair-raising in their galloping momentum. And both players proved subtle interpreters of the serpentine part-writing and intricate rhythms of the four two-part canons Bach appended to his design.
As the astonishingly intricate and chromatic Contrapunctus XI moved grandly to its cadence, we waited breathlessly for the celebrated final, unfinished Fugue on four subjects, including the notes of Bach's name - only to see the players rise, bow and depart.
Evidently, Koopman agrees with his teacher Gustav Leonhardt's view that this final fugue was not part of Bach's original design and should not be performed as such. A pity that was not conveyed to the writer of the programme. Those hoping to experience the dramatic moment in mid-flow when the pen apparently dropped from Bach's hand will have gone away puzzled - and not a little disappointed.