The soundboards of Ruckers harpsichords and virginals were made from a close-grained softwood, probably Picea abies or Picea excelsa. Good stock of these timbers is not easy to obtain these days, but Sykes Timber stock sitka spruce (Picea sitchensis) in long, wide, boards with close grain and completely free from knots or faults. These selected boards (which are not cheap) are used primarily for spars for light aircraft and yachts, and hence are only sold as long boards. I was able to choose a piece 6" x 2", 18 feet long, with perfect quarter-grain and an average of 25 growth rings per inch. This was re-sawn into boards rather less than ¼" thick and 6' long, probably enough for my needs!
The muselaar needed three of these pieces, planed to about 3 mm ready for jointing and final finishing.
When edge-jointing two boards, the edges must match perfectly - it's no good relying on clamps to pull them together. Once the edges are matched, there are several ways of making the joint, but my favourite is to use stretchy masking-tape. This is sold for going round curves, but when stretched and then applied across a joint, it does apply enough pressure to pull the edges together. The other side of this joint was similarly taped, and then a long strip of ordinary tape applied along the joint to stop the glue leaking through. These tapes then formed a hinge, allowing the joint to be opened out to receive the glue. The board was then pressed flat, and the second set of tapes (seen above) applied. Excess glue was wiped off with a warm damp cloth, and then the job left overnight to set.