Tree rings reveal history. They can be used to determine when Vikings first arrived in the Americas. There is a longstanding mystery in the world of multimillion-dollar musical instruments.

By analyzing the wood of two 17th-century stringed instruments, a team of researchers has uncovered evidence of how Antonio Stradivari might have learned how to make violins.

Mauro Bernabei and his colleagues at the Italian National Research Council published their findings in the journal Dendrochronologia, which is consistent with the young Stradivari apprenticing. It has been suggested that there is a link between the two renowned craftsmen.

Stradivari created stringed instruments that were renowned for their quality and sound. Kevin Kelly, a violin maker in Boston who has worked on dozens of violins, said that the best violin maker of all time wasStradivari.

Most of Stradivari's masterpieces are no longer around today. The first such sale in decades is expected to fetch up to 20 million dollars.

ImageAn 18th-century depiction of Antonio Stradivari, the Italian crafter of instruments.
An 18th-century depiction of Antonio Stradivari, the Italian crafter of instruments.Credit...World History Archive/Alamy
An 18th-century depiction of Antonio Stradivari, the Italian crafter of instruments.

Stradivari probably learned his craft by flattery with an older mentor. Cremona, a city in what is now Italy, could have been where that person lived by the mid 17th century.

Mr. Kelly, who was not involved in the new study, said that some people assume that Stradivari apprentices with Amati because he was Cremonese.

There is still no evidence of a link between Stradivari and Amati. Mr. Kelly said that it was the only label like it that has come to light.

Dr. Bernabei and his team analyzed the wood of a small harp made by Stradivari in 1681, in order to shed light on the musical mystery. The researchers used a digital camera to measure the width of the tree rings.

ImageA small harp by Stradivari from 1681.
A small harp by Stradivari from 1681.Credit...DeAgostini/Getty Images
A small harp by Stradivari from 1681.

The pattern created by the plot of the tree rings' width is similar to a finger. Dr. Bernabei said that the amount of trees that grow depends on a number of variables. Plants record their surroundings very well.

The researchers compared their findings from the Stradivari harp with those from other instruments. One of the hundreds of records was remarkably similar to a cello made in 1679. The maximum and minimum values are not unrelated. It is similar to someone splitting a trunk in two.

The Stradivari harp and the Amati cello were made from the same wood. The team concluded that this was consistent with the two craftsmen sharing a workshop.

Mr. Kelly said that it's not the only possibility. He said that Mr. Amati and Stradivari may have bought wood from the same person. In the 17th- and 18th-century Cremona, there was a small community. The people lived on the same street.