Have for a few years come up with their own solutions and been quick to both spread the word and advertise for them. Before I had enough experience and had time to understand what was happening. A big step along the way was an unusually expensive book called "Classical guitar design" by Guiseppe Cuzzucoli and Mario Garrone. It was both a challenge and a revelation to plow through the text which was not the easiest reading! Thought to make a small summary of the book and the special methods I have started to use in my GammelGura.

An acoustic guitar is an extremely complex system. But it all starts with the strings. If you strike a chord on a guitar, you charge the strings with all the power and all the frequencies that then drive the guitar and which are converted into the sound you hear. You can call this package of energy and frequencies a "frequency recipe". In the guitar, nothing will be added to the "frequency recipe", only subtracted, attenuated or redistributed. At each transition between different materials, the recipe is filtered, some frequencies are passed through with little energy loss, others bounce back like a ball against a wall. The first filters that the strings encounter are the upper saddle and the stable leg. On the other side of the filter, a new frequency recipe continues on its way to the next filter where the power has decreased and certain frequencies have been attenuated or redistributed. Here I stop and state that if you want to change the tone of your guitar, you get the greatest effect in the choice of strings and materials in the upper saddle and stable legs. The closer to the strings the more important it is to do the right thing. With that said, of course, the whole guitar that sounds, the ribs, the lid, the bottom and the air volume in the guitar are the "engine" itself that converts a nicely utilized frequency recipe from the strings into something you hear.

My segmented stable leg with spruce between posts of bone gives better string separation between the strings in a chord as the individual strings are allowed to move more freely than on a solid stable leg that connects the strings harder. A thicker stable leg in solid bone also acts a bit like a compressor, at a limit the volume does not increase even if you take in more. The segmented stable leg provides greater dynamics in terms of volume. My experiments also showed that the tone changed if you had spruce or cedar between the posts. The important first filter in the stable leg for the frequency recipe of the strings is different depending on the type of wood that fills in between the leg posts. Cedar gives the guitar a darker tone than the spruce and attenuates more treble. After testing and listening to cedar and spruce on guitars with spruce lids, I got stuck for spruce in the stable leg. Admittedly, cedar sounded good, but I thought something was missing. With spruce, on the contrary, I just got more of the guitar's natural sound, "extra everything". Now I understand that the filter with cedar changes the frequency recipe in a way that does not fit with the spruce lid filter. The stable leg with spruce filters the frequency recipe in the same way as the spruce lid, the same frequencies are passed through or redistributed in the same way. The sound of spruce is amplified. The same with my stable plate in spruce which also gives more of the natural tone of the spruce, the filtering of the frequency recipe of a stable plate in maple is not in phase with the filtration of the spruce.

The stable leg is just the first filter, then we have the transition to the stable, to the lid, to the stable plate and then out to the whole guitar with many more filters. A kind of series connection. The original frequency prescription of the string changes at each transition and what disappears does not affect the parts after the filter. Thus, in order to refine the tone of a guitar, one should strive to have the same material in as many transitions as one can. In a guitar with cedar lid, I would use cedar between the string posts and a cedar stove plate. It is also recognized that the joints and alignment between the parts of the guitar are important. Good fit and a dense and thin adhesive joint provide filters that affect the frequency prescription less than a loose joint filled with thick and tough adhesive. Warm skin glue is recommended, there is no glue that can provide such a strong and dense glue joint between two pieces of wood.

So far the book. What you can take with you is that you never increase on treble or bass with different materials, but instead remove bass and leave treble or vice versa. However, wood of various kinds has a built-in property that affects the tone, internal cushioning. It is a measure of how much energy is converted to heat inside the wood itself when vibrations of different frequencies pass. For example, Rosewood has lower internal cushioning than ebony making rosewood ring more beautiful when dropped on the wood.

A phenomenon that is not talked about in the book or among guitar nerds in general is the importance of making sure that both ends of the strings are firmly mounted and do not yield when a string is struck. Ducking the string at the stop reduces both the volume and the frequency recipe drops trebles. The end of the string is (almost) always very firmly mounted to the metal screw posts of the tuning screw. I now use brackets in metal brackets on all string posts in a notched head. Normally they are only drilled in the relatively soft wood of the head, with metal against metal the contact surface and the attachment become harder and should make the string respond better to the first transient. The profit is there but is probably minimal.

At the other end, on the other hand, the string and the string ball rest on a softer surface. In my case to begin with on a button of hard wood to hold for the wear of the string ball, but then on 6-7 mm soft spruce in the stable plate and lid under the stable in a hard kind of wood and a hard stable leg in the legs. Thought the guitar was too kind and lacked attack. The soft spruce is the Achilles heel and acts as a spring that dampens the transient when the string is fastened. The solution was what I call "turbo plugs", a wooden plug between the string ball and the underside of the stable that replaces the soft spruce with harder wood. Strings that have a fixed mounting at both ends respond better to the transient when the string is fastened with a higher volume and greater clarity from the extra treble.

Everyone knows that a guitar with floating stables sounds both loud and sharp. The reason for this is not the floating stable but the fixed attachment of the string ball to the stable metal string holder. The problem and the reason why the tone is not beautiful in such a guitar is that the thinnest strings get too much treble and volume. When I experimented with plugs, I tested without plugs, only plugs in birch and only plugs in spruce wood in one and the same guitar. Without plugs the guitar was nice but had a soft and beautiful tone. With birch the volume became high and the attack very aggressive, the treble strings cut into my sensitive ears and the tone turned to ugly. With spruces in spruce end wood, which is about 4 times harder than spruce in other directions, the volume increased considerably, the attack became just aggressive but retained the same beautiful tone as without plugs. The difference between the three cases was very big! Later I realized that extra high treble on the bass strings is just good and gives those strings a lovely piano sound and better definition, especially the thick E string. Nowadays I use birch plugs for the two base strings, endwood in pine (which is a little harder than spruce) for the D string and endwood in spruce on the three thinnest.

Can add that the effect of soft or hard string attachment is much greater for steel strands than for nylon strings. The nylon strings lose most of the transient force at the ends of the string as the string stretches all the way to the string ball / tuning post a bit like a rubber band.

Have you read this far, do you know what's going on in my head right now when I think of new ways to improve the tone of my GammelGura guitars. Have a stable made almost exclusively of spruce that I have not tested yet. Maybe should do it…