Making a Bamboo Recorder — A Fipple Flute with a Full Scale

A recorder is a fipple flute: a block in the mouthpiece makes the whistle for you, and a row of finger holes turns that whistle into a full melody.

Pick a straight bamboo tube about 30 cm long and 2 cm across, with smooth walls.

Push out all the inner nodes so air flows freely from the top of the tube straight through to the open bottom.

A few centimetres from the top, cut a small rectangular window with one sharp, clean far edge — the labium. This edge is what makes the sound.

Carve a cork plug to fit snugly in the top, but shave one flat face so a thin channel — the windway — is left along the top of the tube.

Push the block in so the flat channel aims a thin ribbon of breath straight at the sharp edge of the window, with no gaps around the block.

Blow gently through the windway. Nudge the block and trim the sharp edge until you get a clear, steady whistle.

Along the front, mark seven holes spaced to fall under your fingers, plus one on the back for your thumb.

Pierce each mark with an awl and open it out. Start small — you can always widen a hole, but you cannot un-drill one.

Cover all holes for the lowest note and open them one by one to climb the scale. Enlarge a hole slightly to raise its note if it sounds flat.

Both ends of a recorder are open, so it is an OPEN pipe — it sounds about an octave higher than a closed panpipe tube of the same length.

Practise covering the holes cleanly with the soft pads of your fingers. With eight holes you can play a full scale and simple melodies.

A recorder is a fipple, or duct, flute. The block squeezes your breath into a thin flat ribbon and aims it at the sharp edge of the window; the ribbon flaps rapidly above and below that edge (an edge-tone), and this drives the air column in the tube — the same sound source as a panpipe, an ocarina and an organ flue pipe, except the windway is built in so you do not have to aim your own breath. The pitch is set by the length of the vibrating air column. With the far end and the finger holes open, the recorder behaves as an OPEN pipe, whose longest wave is about twice its length, so its frequency is roughly f = v / (2L), where v is the speed of sound. That is a full octave higher than a CLOSED panpipe tube of the same length, where f = v / (4L) — open and closed pipes are the two great families of wind instruments. Opening a finger hole shortens the effective air column and raises the note, and blowing harder makes the column jump to its next harmonic (overblowing) to reach the higher register. Medieval recorders were bored from hardwoods such as boxwood and maple; a bamboo or elder tube gives a simple folk version with exactly the same physics.