Digital Stradivari: computer models of violins reveal master luthier’s techniques

Editor's Note: This post was originally published on the Science at the Smithsonian blog. Learn more about the museum's Stradivari cello.

With the help of a high-resolution CT scanner, researchers at the Smithsonian Institution recently took a giant leap forward to a better understanding of the engineering and craftsmanship that Antonio Stradivari (1644-1737), master violin maker of Cremona, Italy, built into each of his renowned instruments. The CT, or computed tomography, scanner is a medical imaging device normally used in hospitals to create 3-D X-ray images of the human body. 

These two images show measurements of wood thickness on the top board of two different violins used in the study. Red indicates a thickness of 4 millimeters or higher, green a thickness of 2 millimeters or less. Yellow is a mid point between the two thicknesses.

In a pilot study that used seven Stradivari violins made between 1670 and 1709, the researchers scanned each violin with a CT scanner then used the data to create digital, 3-D images of each violin. Using the scanner they recorded exact digital measurements of the dimensions of each instrument; recorded the volume of material used to build each instrument; recorded the volume of air inside the body of each violin; and measured variations in the thickness of the thin layer of wood that makes up the top board and back board in each instrument. A number of the violins used in the study are from the collection of the Division of Musical Instruments of the Smithsonian’s National Museum of American History. The project was a collaboration between the American History Museum and the Smithsonian’s National Museum of Natural History. 

Many intricate and previously unseen details were revealed in the digital images, such as repair patches in a violin’s interior, the exact yet subtle slope of each back and front board, and the location of ivory and ebony inlays. Most importantly, when the data for each violin was compared, the researchers could see how the manufacture of the violins changed over time. 

“The use of the scanner has improved our access to research data which otherwise would be inaccessible,” says Bruno Frohlich of the Anthropology Department at the Smithsonian’s National Museum of Natural History. “Obviously, we cannot take these instruments apart and study how they were made. Yet the digital models made with the scanner are factual representatives of the original objects and allow us to study how the instruments’ general architecture and other features have changed over time.” 

This 3-D model reveals the shape and volume of the air mass located inside the body of a Stradivarius violin.

One discovery the team made was that the volume of wood made in the construction of the violin bodies varied by 41.6 percent from 1670-1709, yet, the volume of air inside the violin bodies varied by only 8.2 percent. “Stradivari tried to keep the air volume in his violins as constant as possible, even as the trend of construction over time moved in the direction of a thinner wood board,” Frohlich says. The thickness of wood used in the construction affects the weight of the instrument, the strength and possibly tone. 

With the success of the pilot study, the researchers now plan to analyze and compare data collected from scans of 47 other old instruments made by Stradivari, Nicolo Amati, Joseph Guarneri and other luthiers. When compiled this data should tell an interesting story of how violin making has changed, or remained remarkably the same, in the last 350 years. 

 The research team included Bruno Frohlich, Gary Sturm of the Division of Music, Sports and Entertainment at the National Museum of American History; Janine Hinton, of the Department of Anthropology, National Museum of Natural History and Else Frohlich of the Department of Biomedical Engineering, College of Engineering, Boston University. Support for the project was provided by Siemens Medical Solutions in North Carolina and Materialise in Belgium and Ann Arbor in Michigan.

Comments

[Pearl Deans]

Mr. Bruno Frohlich:
It may not be necessary for modern instrument makers to copy the instruments made by Stradivari. But I think the more pertinent question is, is it desirable? I can imagine there are at least one or two master instrument makers who would love to use modern technology to make replicas of the instruments made by Stradivari.

[Jennifer]

Wow that is extremely interesting. I'd like to see this same study done on different brands of guitars.

the violins described above are solid-body models. This means that the instrument has no hollow, resonating chamber and therefore produces little to no sound unless it is "plugged in." However, another way to create an "electric violin" is to replace the bridge on an acoustic violin with a piezo pickup bridge-mount that can be plugged in just like a solid body.

[Steven DeBardelaben]

Does this study take into account the density of the wood? I have read a theory that for a century or so, the period of time before Stradivari was born, was a time of colder temperatures in Europe. The theory was that this resulted in different growth process in the trees. There was discussion that some of the tone richness from his instruments was due to the density of the wood that grew in this cold period. This was supposed to be the wood that Stradivari used.

I never heard of this theory being explored further.

[NMAH]

About the size of the instruments:
Unfortunately the two images of the top boards may suggest different sizes. Actually they are of the same size. One amazing observation with violin metrics is that there is very little variation in the size of the instrument over time. We find that older instruments may have a more significant curvature on the back and top boards whereas more modern instruments may show a more flat shape. I believe that some of this change took place during Stradivari's time. The purpose may have been that by utilizing less curvature the instrument maker could make the boards thinner and still keep the constructional strength required for the instrument to be functional. Thus it may be that the direction from more curvature to less curvature could be a product of the desire of producing a lighter instrument. The volume or mass of the wood will decrease while the volume of the air mass within the body may stay almost the same.

Bruno Frohlich

[NMAH]

Mr. Pablo Sacco:
I agree with Mr. Saccos statement. It is not necessary for modern instrument makers to copy the instruments made by Stradivari. High quality modern instruments following the traditional ways of manufacturing are master pieces in their own ways and will most likely produce an excellent sound quality if played by an expert musician.
Bruno Frohlich

[NMAH]

Mr. Michael:
I am not exactly sure why some modern instrument makers are so interested in telling people that he/she is making copies of the original Stradivari instruments. I think it is marketing more than anything else. One problem with making copies of Stradivari's instruments is that we do not know how many repairs and/or changes may have been done over the years. The instrument we see today as a Stradivari instrument may have little similarity with the instrument produced by Stradivari more than 300 years ago.

Bruno Frohlich

[NMAH]

Dear Mr. Altmaier,
The color displays are reflections of the thickness of the wood used in the construction of the instruments. Thus red colors indicate higher thickness values and green colors smaller thickness values. Any additional pieces of wood, which may have been attached on the inside of the body, will show up as higher thickness values(toward the red color). In some of the instruments we see many small squares suggesting patches which have been added to repair or prevent cracking of the wood. The long lines represent the 'bass bar'. This is a long narrow piece of wood, most often soft wood, glued to the inside of the top board. The bass bar should improve the sound production and is found in all violins and violas. I hope this answers your question.
Thank you for your interest in our research

Bruno Frohlich

[Ralph Altmaier]

I am wondering if the vertical line in the scans is an artifact of the process. I see it in all of the scans. There are 2 thicker places between the f holes that I see on most of the violins. Can you provide some thoughts on these thick spots?

[Brian]

I don't see the problem with making copies of the these great instruments. One would only hope that the newer models would last many years so that future generations can enjoy playing and or admiring the great works of musical art peices. I doubt that these old violins will be around another 100 years in a state that they could be played without the risk of damage. Just my thoughts on the matter for what it's worth.

[Michael]

I only hope that violins manufacturers will not start to exploit these discoveries in order to produce new "original" Stradivari instruments.

Some things should remain perfect as they were. No need to make replicas of these perfections... :(

[Pablo Sacco]

I would like to know the measures of the violins under test. I can immagine they are different. Does it mean he had to raise the heigjt of archings and ribs if the instrument is shorter or narrower?
Other factor to consider is the pass of the time and restorers in that time. There's no Strafivari's instrument exactly the same as he constructed them. When somebody "reshape" the thicknesses of the plates, that produces a very big impact in the volume of the plate itself, while that cents of millimeters affect only a few in the total amount of the air volume inside the body.