Shakuhachi (尺八) is a Japanese flute which is end blown as opposed to transverse. Tuned to a pentatonic scale, although capable of playing pitch on the chromatic scale as well, it was used by Zen Monks in the practice of Suizen (blowing meditation). It is usually made from the root end of bamboo and, despite having only 5 holes, is a very versatile instrument. This is because holes can be covered only 1/3, 1/2, 2/3, etc., and pitch varied subtly by changing the blowing angle. Professional players can produce virtually any note they wish from their shakuhachi, an interesting example of classical-level technique applied to what is still in essence a simple folk instrument.
The name shakuhachi is derived from "shaku", which is an archaic measure of length about 30 cm long, and "hachi", which means "eight". Thus the standard shakuhachi is 1.8 shaku in length, or 54 centimeters. However, shakuhachi vary in length from about 1.3 shaku up to 3.3 shaku. Although the lengths differ, they are all still referred to generically as "shakuhachi".
The bamboo flute first came to Japan from China via Korea (like much of Japan's "high culture"). The shakuhachi proper, however, is a quite distinct from its continental ancestors, the result of centuries of isolated evolution in Japan.
During the medieval period, shakuhachi were most notable for their role in the Fuke sect of Zen monks, whey used the shakuhachi as a spiritual tool. Their songs (called "honkyoku") were paced according to the players' breath, and were considered meditation as much as music.
Travel around Japan was restricted by the shogunate at this time, but the Fuke sect managed to wrangle an exemption from the Shogun, since their spiritual practice required them to move from place to place playing the shakuhachi and begging for alms. In fact, they persuaded the Shogun to give them "exclusive rights" to play the instrument! In return, however, they were required to spy for the shogunate, and the Shogun sent several of his own spies out in the guise of Fuke monks too. (This was made easier by the baskets that the Fuke wore over their heads, a symbol of their detachment from the world.)
In response to these developments, several particularly difficult honkyoku pieces became well-known as "tests": if you could play them, you were a real Fuke. If you couldn't, you were probably a spy and might very well be killed if you were in unfriendly territory. This no doubt helped drive the Fuke sect to the technical excellence they were renowned for.
In any case, when the Meiji Restoration occurred in 1868, the shogunate was abolished and so was the Fuke sect, in order to help identify and eliminate the shogun's holdouts. The very playing of the shakuhachi was officially forbidden for a few years. Non-Fuke folk traditions did not suffer greatly from this, since the tunes could be played just as easily on another pentatonic instrument. However, the honkyoku repertoire was known exclusively to the Fuke sect and transmitted by repetition and practice, and much of it was lost, along with many important documents.
When the Meiji government did permit the playing of shakuhachi again, it was only as an accompanying instrument to the koto, shamisen, etc. It was not until later that honkyoku were allowed to be played again as solo pieces.
