It's advantageous to think of the utaguchi (the blowing edge) as a hole. Because while the shakuhachi is played, in fact, a hole is formed by the utaguchi on the flute and the players lips. And this hole, the Sixth Hole as it were, produces the soul of the shakuhachi. Why? Because the utaguchi hole is adjustable and during normal shakuhachi play the shape and area of the utaguchi hole is constantly varied. That's what meri-kari is--the most obvious sonic effects of changing the shape and size of the utaguchi hole. Make the hole smaller and the pitch drops, larger and the pitch rises. So again, as with many things shakuhachi the action is defined by what isn't there instead of what is. The emptiness rather than the object. So focus on what's beyond the utaguchi rather than the edge itself. The edge defines one half of a hole, your lips the other half. And the shape and size of that hole is vitally important to the sound quality of your shak. If the utaguchi isn't right, the rest of the flute is vastly under utilized.

While creating some Watazumi flutes (you know, those big long suckers) difficulties developed immediately while trying to get a good Ro. And they were traced to the utaguchi--the blowing edge. After some research, it was realized that proper utaguchi design requires the width to be about 1/4 of the circumference of the bore average and utaguchi depth should be about 1/5 of the width. For the size pipes (the Watazumi models) we were using, lips couldn't create an airstream wide enough for a proper utaguchi. So adjustments have to be made on extreme utaguchi widths, otherwise the graph below will suffice.

In general, the utaguchi hole's area is about two-thirds that of any other hole. And area is where the action's at. The utaguchi doesn't cleave the airstream so much as form one side of a very supple and adjustable hole. Sharpening the utaguchi doesn't help anything particularly and can create unwanted noise the same as any other shape edge. For optimum operation the hole created by the utaguchi must be correctly coupled (by area) to the air volume in the bore. So the size of the utaguchi naturally increases as flutes lengthen. When area is properly matched to volume, bamboo sticks start to sing.

A narrow and/or shallow utaguchi favors the harmonics and upper registers and lowers the pitch. Until we got the shape and size right one of the Watazumi pipes was playing third octave and only by extreme coaxing would first octave and the fundamental appear. A wider deeper utaguchi favors the lower register and the fundamental portion of the sound envelope and raises the pitch.

There seems to be some confusion about the size of the utaguchi hole and its effects on harmonics and pitch. Here's the thing: Imagine that the hole got smaller and smaller until it finally closed (ignoring for the moment that the flute is driven by air passing over or through the hole). Closing the end of a tube cuts the frequency (pitch) in half. So smaller hole is lower pitch. Something else happens with a closed tube, the even numbered harmonics drop to zero and vanish. So the shakuhachi is somewhere between an open and closed tube and by varying the degree of opening (the size of the utaguchi hole) the sonic and acoustic qualities of the flute are altered. Meri closes the hole thereby lowering the pitch and reducing the intensity of the 2nd, 4th, (etc.) harmonics. In particular, reducing the second harmonic makes the tone sound thin. Kari opens the hole, thereby raising the pitch and boosts the even numbered harmonics for a richer, fatter sound--thus a fuller Ro. That's what happened with the Watazumi pipe--it's pitch rose a full note. And utaguchi size and shape sets the degree of your flute's inherent kari-meri--the point from which literal kari-meri deviates. The utaguchi determines the inherent degree of open/closesness a flute possesses--thus its sonic properties and capabilities.

Contrary to ordinary intuition, it's possible to design a flute where the first and third octaves play better than the second--in a relative sense. How is this possible? By clamping down on the size of the utaguchi hole, the first and third harmonics remain and are strengthened, while the second harmonic is depressed. And second octave is just shifting the flute to second harmonic. If it's naturally weak, so to will be second octave. That's what we stumbled onto with the Watazumi tube and its undersized utaguchi. So it follows that a flute which has a strong third octave does so at a cost to the second. And that's the charm and penalty of flutes with high Aspect Ratios--improved upper register and weak mid-register (second octave). In the end, much of the talk about harmonics and fundamentals comes down to the ratio of the amplitudes of second and third harmonics. A strong second tends to be described as a flute with a good fundamental. A weak second, thus a strong third, tends to be described as a flute with good harmonics as its sound is the result of higher harmonics. (see more about Harmonics) Also the Harmonic Series.

The sound quality and playability of a flute can be altered dramatically by changing the utaguchi's geometry--thus the hole size and shape. To such an extend that it's surprising that someone has offered flutes with adjustable utaguchi. A utaguchi which could be extended and retraced could change a simple flute into a racehorse. This is the place where a millimeter make a big difference. An adjustable utaguchi would give your flute several personalities or allow them to be revealed, however you want to think about it.

Ever wonder why the same flute sounds different when played by various people? One of the reasons is the variation in lips, thus variations in the size and shape of the utaguchi hole thus differences in the sound. Flutes usually achieve optimum performance only with lips exactly like that of the maker. But what percentage of the population does that encompass? An adjustable utaguchi would put a lot of myths and misinformation to rest.

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