Growing up in a village in Kagawa Prefecture on the island of Shikoku, Masashi Tomikawa never thought twice about the geology of his surroundings. The volcanic rocks that surrounded him, however, are now part of the drummer’s arsenal of sound.

“In my village the rocks have been used since ancient times,” Tomikawa says. “But people outside of Shikoku have often never heard of them.”

The black sanukite stones, known locally as kankanishi (cling-clang rocks), have been used to make tools for more than 10,000 years. When Tomikawa was a young boy, he recalls teachers taking elementary and junior high school students up the slopes of Mount Kanayama in Kagawa Prefecture to collect the rocks — just as his grandmother was forced to do during the war, when the stones were used as part of the protective armor for military aircraft.

“The sanukite stones of Kagawa Prefecture are more than 13 million years old,” Shuichi Hasegawa, a professor at Kagawa University, tells The Japan Times. “They are much harder and finer-grained than ordinary volcanic rock, and can only be found in four locations in Japan: Kagawa, Nara, Osaka and Hiroshima prefectures. Although stones from all four areas can produce a sound when struck, the ones from Mount Kaneyama have a higher absorption and P-wave velocity, thereby producing the fullest tone.”

That tone sounds similar to the resonant sounds of a large bell or gong, but slightly higher pitched. Tomikawa uses the rocks as percussion instruments in his jazz ensemble, Yume-Goto.

The stones have been used in musical performances before, most notably in the 1970s and ’80s by musician-turned-Buddhist-priest Tsutomu “Stomu” Yamashita and currently by percussionist Reiko Komatsu. Additionally, sanukite expert Hitoshi Maeda has created four types of instruments from the stones: a kind of xylophone called a sekkin; hanging bell-shaped stones called sou; uncut field stones called rou; and hanging gong-shaped stones called kei. Maeda has been showing off these instruments to visitors for more than 30 years, and says they’ve always impressed the musicians, artists, scholars and historians who’ve seen them. However, the Sakaide City Cultural Office maintains that even though they have frequent demonstrations and some smaller stones are available for sale locally, their treasure remains mostly unknown abroad and even within the rest of the country.

Tomikawa has decided this needs to change. Along with shakuhachi player Hirofumi Miyazaki he formed the quartet Yume-Goto (rendered roughly in English as “The Thing of Dreams”) in an effort to incorporate the stones’ sounds into a casual performance setting and expose them to a broader audience. Both men are Kagawa natives, and Tomikawa says this had been a project they’d been speaking about for a while. Miyazaki owns land on a mountain in Kagawa that has deposits of sanukite, and as the owner of a small construction company has access to equipment that can transport the very heavy slabs to a local stone factory for cutting. He then had them arranged into a hanging set that gets placed next to Tomikawa and his regular drum kit on stage. Rounding out Yume-Goto are Tomikawa’s frequent collaborators, Japan-based American musicians Neil Stalnaker and Jeff Curry, on trumpet and bass respectively.

“We didn’t approach this group with the set idea of it being either a Japanese or Western group,” Tomikawa says. “Rather, we wanted to capture the reaction of musicians from both cultures as we came together to play. Miyazaki used to be a jazz guitarist and I’m a jazz drummer so we’re both familiar with Western styles as well as Japanese instruments such as the shakuhachi. Neil and Jeff live in Japan but bring their own American sensibility to the improvisational process. Although Miyazaki-san cannot speak English, Neil and Jeff are both incredible musicians who can take the barest of musical cues from the shakuhachi and respond eloquently.”

Yume-Goto are very much an improvisational group. At a show, the large, hanging pieces of stone on stage are struck by Tomikawa, the shakuhachi comes in and an effects-laden trumpet soon follows. The effect of seeing the black and gray slabs of rock on stage is striking, it adds an almost mystic quality that gives off the feeling of a religious ritual, which is further enhanced by the traditional sound of the shakuhachi. The listener is transported to a place that is unmistakably Japanese, but then more familiar shapes and patterns slowly start to develop into recognizable jazz structures with swinging rhythms. The result is ethereal music with a strong jazz foundation. The name Yume-Goto is fitting.

“The name was given to us by Miyazaki’s neighbor in Shikoku, a Japanese calligraphy master,” Tomikawa says. “He and Miyazaki drink together quite often and one time Miyazaki spoke of his dream to create this band. The master immediately got his brush out and wrote the characters for yume (dream) and koto (thing).”

Since Miyazaki is based in Shikoku and the heavy stones are difficult to move around, the band rarely play in Tokyo. However, they hope to figure out the logistics of being able to take their music overseas.

“This pure sound within our group’s music, we want to share it,” Tomikawa says. “We want to reveal the spirit of time itself that’s contained within these ancient stones.”

Masashi Tomikawa jams regularly at venues across the country. His next session will be at Ikebukuro Field in Tokyo on Nov. 19. For more information, visit www.masashitomikawa.com. For more information on the sanukite stones, visit www.sanukite.com .