Of all Japan's own instruments, the shakuhachi, a simple five-hole, end-blown flute made from the root end of a bamboo stalk, has achieved the greatest success beyond these shores.

End-blown flutes of several kinds were introduced from China during the Heian Period (794-1185) as part of the gagaku court orchestra. Subsequently it fell out of use in this context, however, and the Heian shakuhachi music is essentially lost. The music that has won so great a following today is based on the repertory of the medieval wandering flute-monks, the komuso, who by the 17th century were organized into a mendicant Zen order which used the instrument as a form of meditation.

At the same time it developed an amateur following which practiced it purely for musical enjoyment, and the 20th century saw a great deal of new composition for the shakuhachi in various styles.

Modern shakuhachi master Akikazu Nakamura is a graduate of Berklee College of Music and the New England Conservatory in the United States, where he studied composition and jazz improvisation. He has been active both in Japan and abroad in modern music, and attracted considerable attention with the album "Zoom," recorded by his group Kokoo including koto players Michie Yagi and Miki Maruta, which included a work by King Crimson.

Despite these influences, Nakamura is firmly rooted in the shakuhachi's classical honkyoku repertory, and his solo album "Saji" demonstrated to any doubters his command thereof.

"I've always had that kind of soul," he emphasizes. "Even when I was playing with jazz or rock people in New York, I was always thinking about expressing my Japanese soul. I always kept a feeling of Japanese sound, and tried to adapt my sound to jazz or rock."

If "Saji" emphasized the Zen classics such as "Tsuru no Sugomori" and "Shika no Tone," Nakamura's latest album, "Tsugaru no Shakuhachi" (to be launched with a concert at Casals Hall Oct. 25), explores a more esoteric byway of Zen shakuhachi: the Nezasaha Kinpu-ryu, a special lineage fostered by the music-loving lords of the Tsugaru area at the north end of Honshu. Its style is characterized by the assertive beat that is a prominent feature in other Tsugaru performance styles such as Tsugaru shamisen.

The Nezasaha Kinpu-ryu has an unusual history among shakuhachi schools. The music-loving ninth lord, Tsugaru Yasuchika, as part of his efforts to raise the cultural level of his remote domain (he also founded a college there), dispatched one of his samurai, Yoshizaki Hachiya (1796-1875), to learn the komuso shakuhachi at the important Fuke sect temple Ichigetsuji in what is now Chiba Prefecture. Yoshizaki returned home in 1818 as a shakuhachi master with the name Kodo, and taught the music to other samurai of the domain.

Komuso in general were considered a low element in society, little better than wandering beggars, but since Kodo's students were all fellow samurai, their music acquired social cachet. At the same time, they were samurai of far Tohoku, and the deep, throbbing beat of the Tohoku spirit infected their work. From the Meiji Era the Nezasaha Kinpu-ryu found followers throughout the country.

In exploring the Tsugaru repertory Nakamura is following in the footsteps of his teacher's teacher, the late shakuhachi legend Watazumi Doso, perhaps the 20th century's greatest proponent of the instrument as a route to enlightenment. Determined to track the Tsugaru style to its roots, Watazumi Doso spent an extended period in Tsugaru learning the Nezasaha Kinpu-ryu.

The Nezasaha Kinpu-ryu special repertory comprises 10 pieces, including versions of komuso standards like "Shirabe," "Hachigaeshi" and "Koku," but with some more unusual pieces like "Shishi (Lion)" and "Sagariha (Ebbing Waves)." The Bodhisattva of Supreme Wisdom, Manjusri, is usually depicted mounted on a lion and carrying a sword, representing the power and suddenness of enlightenment. "Shishi" expresses this in its forceful melody, which also shows influence from the flute music of festival lion dances.

"Sagariha" similarly is a high-energy piece, using the komi-buki vibrato technique to express the feeling of wind and waves.

In Nakamura's view, Watazumi Doso brought the vigor and power of the Tsugaru style to his entire repertory, using it to re-interpret and revivify the classic honkyoku.

"I feel that this technique and this spirit is kind of my 'lost soul,' " Nakamura says. In search of it, he literally followed in Watazumi Doso's footsteps -- he went to Tsugaru and sought out elderly players who might remember who the mystic master had studied with, and could teach him likewise the authentic secrets of the samurai shakuhachi of Tsugaru. The results of these efforts can be heard on his new album, and at next week's recital in Casals Hall.