Building a Sheng — The Chinese Free-Reed Mouth Organ

The sheng is a mouth organ: a bundle of bamboo pipes standing in a wind chamber, each voiced by a tiny springy reed. It is the world's first free-reed instrument and the ancestor of the harmonica and accordion — and it can play chords.

Hollow a dried bottle gourd into an airtight air-chamber and fit a short mouthpiece tube into its neck to blow through. Early sheng used a gourd just like this.

Cut several thin bamboo pipes of different lengths. Start with five or six — enough for a small scale or a couple of chords.

Near the bottom of each pipe cut a small, clean rectangular window. The free reed will sit over this window.

From thin brass, cut a tiny tongue that ALMOST fills a matching slot — fixed at one end, free at the other, with a hair-fine gap all around so it can swing cleanly through.

Seal a reed over each pipe's window with wax, airtight, with the free tongue facing inward toward the chamber.

Cut one finger hole in the side of each pipe. This little hole is the on/off switch for that pipe's note.

Push the pipes down into the top of the chamber and seal each with wax so NO air can leak except through the reeds themselves.

Blow gently into the mouthpiece and cover one pipe's finger hole. Covering the hole forces the air through that pipe's reed, and the reed sings out.

With the hole OPEN, air just escapes and the reed stays silent. COVER the hole and the pipe sounds. That is how you pick out notes on a sheng.

Add a dab of wax to a reed's tip to LOWER its pitch, or file the tip thinner to RAISE it, until every pipe is in tune. The reed sets the pitch, not the pipe length.

Cover several finger holes at once and blow. The sheng sounds them all together as a chord — something almost no other wind instrument can do.

Now breathe IN through the mouthpiece. Free reeds sound on both blow and draw — the very trick the harmonica borrowed from the sheng.

The sheng is built on the free reed: a thin springy tongue that vibrates freely back and forth THROUGH a close-fitting slot, instead of slapping shut against a frame like the beating reed of a clarinet or the buzzing lips of a horn. Air flowing past the tongue sets it swinging in and out of the slot, chopping the airflow into a steady tone at the tongue's own pitch — and because the tongue passes cleanly through the gap, it speaks equally well whether you blow or draw, which is why the sheng and its child the harmonica both play in and out. Each reed is paired with a pipe whose air column reinforces it, and the finger hole is a switch: only when the hole is covered is the air forced through the reed, so a player can pick out notes, and several at once, giving the sheng its rare power to play chords. Pitch is set by the reed's length, thickness and a tuning dab of wax — not by the pipe's length. The sheng has been played in China for some three thousand years, and when examples reached Europe around 1800 they sparked a whole family of Western instruments: the harmonica, accordion, concertina, harmonium and reed organ all descend from this gourd full of singing bamboo. Its distant cousin is the jaw harp, whose plucked springy tongue is the same free-vibrating idea, driven by a finger instead of by breath.