Thoughts on the Harpsichord
The vibrations of a soundboard can be compared to the waves of the ocean. If waves wash onto a flat shore, they peter out. However if they pound against cliffs, they are thrown back and form new waves.
When building a harpsichord, the vibrations are influenced by the bellyrail's properties. If the bellyrail is flexible, the vibrations of the soundboard diminish quickly. This gives the instrument a short, clear sound. If the bellyrail is more rigid, the energy caused by the vibrations reforms again and again, giving the instrument a fuller and longer sound.
Merely by choosing the rigidity of the bellyrail, the harpsichord maker determines how soft the instrument's sound will be depending on what is needed or required. Other factors that will influence the sound are the strength of the soundboard, the soundboard bar, the choice of woods and, of course, the instrument maker's abilities.
Since the 80s, we have endeavoured to visualise the vibration behaviour of instruments. As part of our research in cooperation with the University of Karlsruhe, a student wrote a model analysis program for us as his final-year thesis. Since then we have been able to display the vibrations of our instruments' soundboards and also to document the changes in vibration behaviour when we make modifications.
A further important aspect of instrument making is how different forces affect the case when tension is placed on the strings. In a two-manual harpsichord with three stops, the instrument is subjected to around a ton of tension which the internal construction has to contain. The fact that this is not always successful can be seen in examples of strongly deformed and torn soundboards the weakest link in the chain. We have also broken new ground in this area, and, with the help of a structural engineer from the University of Applied Sciences in Karlsruhe, we have been able to optimise the internal construction of our original harpsichords, taking acoustics and statics into account.
Ultimately, a musical instrument is such an incredibly complex structure from a physical point of view that it will probably never be possible to investigate in detail all of the factors which affect the sound of the instrument and which will continue to occupy an instrument maker for life.