The claviorganum was the largest and most complicated of the chamber keyboard instruments. Few have survived in their original state, although traces remain to show that many harpsichords had an organ which has since disappeared.
Extant claviorgana include the 1585 Alexander Bortolotti currently housed in the Conservatoire Royal de Musique, Brussels, Belgium, the Ludovic Theeuwes instrument of 1579 in the Victoria and Albert Museum, London and the 1750 Kirkmann-Snetzler belonging to the Earl of Wemyss of Scotland. It is said that there may be as many as 35 others in various collections and museums throughout Europe and even Latin America - taken there by the Spanish.
It would appear that all surviving claviorgana have only one or two keyboards and are permanently joined together in the sense that if the harpsichord were to be removed, there would be no keyboard available to play the organ that remained and I was keen to overcome what appeared to be a severe limiting factor.
I found the answer to this problem in the writings of the eighteenth century Parisian authority Dom Bedos (François Bedos de Celles). His L'Art du Facteur D'Orgues of 1768 contains very clear details (his plates CXXXIV and CXXXV) of how a claviorganum can be constructed with three keyboards - two for the double manual harpsichord and one for the organ itself how the coupling can be arranged between the harpsichord and the organ and the pipes accommodated within the organ case.
Despite this neatly documented and illustrated information, to my knowledge nobody had ever built such an instrument, so I decided to use his material to make one. It was an exciting idea to take something which had lain undisturbed since the eighteenth century as just print on paper and turn this into a reality. This was achieved with the vital help of the organ makers John Bowen of Northampton and Robert Shaftoe of Pavenham, Bedford.
Double manual.2x8'+1x4'+lute, Five octaves-GGto g3
Sliding upper manual shove coupler
Diapason at eight foot pitch: Stopped - GG to g3
Four foot flute - Stopped - G to f#1, Open -g1 to g3
Two foot principal - Open - GG to g3
Sesquialtera - Open G to g3 (12th)
Mixture - Open - c1 to g3 (17th)
Single manual shove coupler to harpsichord above.
Four draw stops.
There is now a CD available which demonstrates the scope of this instrument. It contains five of Handel's organ concertos (numbers 8, 9, 10, 11 and 12, opus 7) performed by the SWR Orchestra of Kaiserslautern conducted by Klaus Arp with the soloist Alfred Gross on the Koch-Schwann label - number 3-1122-2