PGM owns a two-manual harpsichord, built by Tyre & Goudzwaard, Grand
Rapids, MI., specifically designed for the performance of
seventeenth-century music.There is a painting of Buxtehude and Reincken at a harpsichord which appears to be a double-manual instrument in which the upper manual definitely stops before arriving at the lowest notes, thus making it about five notes less than the lower manual.
Originally, harpsichords like this were built with the keys unaligned, so as to make the upper manual play at normal pitch, and the lower manual at a pitch a fourth lower than that written. The original use of this strange device is not known, and even speculations have to be guarded. In any event, lots of instruments of this type were made in the two generations before Buxtehude.
By Buxtehude's time however, whatever the purpose served by the transposing was apparently no longer germaine to keyboard music performance, and most of the double-manual instruments were eventually changed and enlarged into what we now call the "French" format. The upper keyboard had notes added to it in the bass, and a second 8' string was installed for each note so that on the lower keyboard two 8's and one 4' were available, and on the upper keyboard only a solo 8' string. The lower keyboard was moved toward the treble by five chromatic notes by removing the extra five keys from the treble and re-installing them as bass notes.
There are, however, two surviving instruments in which the keyboards were aligned without adding the missing notes at the bass of the upper manual, and no additional 8' choir of strings was installed. This produces two keyboards which each play 8' and/or 4' at the same pitch, but also two keyboards with differing bass octaves. The upper keyboard continued to look as if it ended at low E, while the lower keyboard had a fully chromatic bass down to C or BB.
There are suites by Buxtehude in which, in one movement, the music can only be played on this kind of short-octave keyboard, which brings low D for instance within the reach of tenor f#, thus permitting fingerings impossible on a full chromatic keyboard. But in the same suite, a different movement has a low F# in the score, and that is the note that sounds as D in the upper keyboard. So the player would have to have two different styles of keyboard, both aligned for the same pitch, in order to be able to play the suite without having to re-tune notes from time to time.
So it is quite likely that Buxtehude had, at one time or another, access to such a harpsichord and tailored music to it.
The instruments we have used as models are three by two brothers, Ioannes and Andreas Ruckers. We have used the string scalings from an instrument currently in Edinburgh, Scotland, in the Raymond Russel Instrument Collection of the University of Edinburgh. It was built by Ioannes Ruckers at the age of 61 in 1638, in Antwerp. This instrument's scalings show no evidence of any later adjustments, so they are best to follow.
But for additional construction details we followed features of a 1640 instrument by Ioannes currently in the Schloss Ahaus in Westphalia, Germany, and also of another 1640 instrument by his younger brother Andreas, which is now in a hotel in Namur, Belgium. The Schlaus ahaus instrument was originally purchased by the count who lived in that castle, and the instrument has been in that title'd family's hands ever since.