The profound limitations to Dr. Harris’ work have shown up too in Jo Curtin’s work, published in The Strad Journal: see this page and revealed by his his article on Strads. The effects of gluing each plate to the stiff bouts seems to dominate!
As I said, I have concentrated on getting the tap tones of the plates where I want them, but tap-tones are just a part of the whole: the air volume, f-hole area, arching, body length, sound-post and bridge must all be right too.
My findings so far are that Carleen Hutchins broadly got it right: if you set the Mode 5 tap tone of front and back with the belly just a few Hz below the back at 340 to 350 Hz (measured with low moisture content in the wood), your fiddle can turn out sounding good!
To get more consistent results, especially helpful for beginners, the other change to traditional practice the Mr. Kreit introduces is measuring and setting what he calls the Coupling Frequencies.
There are two Coupling Frequencies are the tap tones or resonant frequencies measured when
1) just the back plate is glued onto the bouts (or garland) and without the neck attached, and then
2) just the belly is glued onto the the bouts (or garland)., again without the neck.
These are easily and quickly measured, but do require that one of the plates is first temporarily glued (using diluted weak glue and cigarette papers!) to the bouts or garland, and then removed before the other plate is glued to the garland.
This puts an important intermediate step between setting the tap tones of the pates and then setting the difference between the coupling frequencies of back and belly to about 25 Hz, as shown in the important chart on the right. Click on it - it is a .pdf file.
So for a violin made from scratch, that is started from blocks of wood, I can measure the 19 different frequencies of the individual parts and then also the final body-mode frequencies of finished violin. So the instrument ends up with the key body resonances just where I want them.
The chart I use to do this now for all my violins is here on the right - click on it: it is important.
Does it matter if violin plates are heavy even though they are tuned to the right Mode 2 and 5 resonant (tap tone) frequencies?
Well, yes it does, and a lot. The weight, or rather the lightness of each plate is a measure of its quality, providing that it has the right tap tones and low losses when it vibrates. A light plate with the right arching and thicknessing on good wood has less wood for the bow and strings to move: it will respond more quickly and give out more sound energy.
If you have a look at the page on ‘Plate tuning 4 dummies’ I show you how to make the best of the wood or plates you have to make a violin that will sound very good indeed, but there is no substitute for buying the best low density stiff wood you can afford!
‘Ordinary’ wood will make a good violin (as the Chinese student violins now show!) provided you get the plate tap tones right!