Why Does a Recorder Play Itself? The Mouthpiece Does the Hard Part

A block of wood or plastic fills most of the top of the instrument, leaving a narrow slot between it and the wall, and that slot directs the player's breath as a thin flat jet along the inside of the tube towards an opening cut in the side. The far edge of that opening is cut to a sharp edge, and the jet strikes it. Air arriving at a sharp edge is unstable and flips from one side to the other repeatedly, and the column of air in the tube governs how fast it flips, so the tube's own resonance controls the pitch and the jet simply supplies energy.

Building the jet into the instrument removes the hardest part of learning:

• •The player supplies breath and nothing else to make a note
• •No embouchure is needed, which is what defeats beginners on a flute
• •A note sounds on the first attempt, reliably
• •Pitch comes from finger holes and from breath pressure only
• •The same design appears in whistles, flageolets and organ flue pipes
• •The trade is that the player cannot shape the jet at all

Fixing the jet removes the control that a transverse flute player has, and that limitation defines the instrument's character. A flute player directs the air with their lips and can change its speed, angle and width continuously, which allows large changes in volume without changing pitch, a wide range of tone colours, and expressive bending of notes. On an instrument with a built-in jet, blowing harder raises the pitch as well as the volume, so dynamics and intonation are locked together and cannot be varied independently. Players compensate with fingering adjustments, partially covering holes and shading, which is a real skill and does not fully recover the range.

A church organ contains hundreds of pipes built on exactly this arrangement and understanding one explains the other. Air from the wind chest passes through a narrow slot, is directed as a flat jet at a sharp lip cut in the pipe wall, and sets the air column vibrating, which is the same mechanism at a larger scale and with the air supply mechanised. That is why such pipes are called flue pipes, and why they are voiced individually by a specialist who adjusts the width of the slot, the position of the lip and the shape of the jet to control tone and speech. Reed pipes in the same instrument work quite differently, using a vibrating tongue.

The recorder was standard in Renaissance and baroque music, was displaced almost entirely by the transverse flute during the eighteenth century, and returned in the twentieth for two quite separate reasons. The early music movement revived it for the repertoire written for it, and serious players and makers rebuilt the craft from surviving instruments and treatises. Separately, and far more numerously, it was adopted for school music teaching precisely because the built-in jet makes it playable immediately, cheap to manufacture in plastic and capable of ensemble work within weeks. Those two populations of players have almost nothing in common, which is why the instrument has such a divided reputation.

A block leaves a narrow slot that aims the breath as a flat jet at a sharp edge, where it flips back and forth at a rate the air column in the tube controls, so the tube sets the pitch and the player only supplies air. That removes the embouchure entirely and makes a note sound on the first attempt. It also locks volume to pitch, which a flute player can separate and a recorder player cannot.