PHILIPPE BOLTON, RECORDER MAKER

Medieval, pre-baroque, and baroque recorders

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HOW RECORDERS WORK

THE RECORDER'S MOUTHPIECE

section view of a baroque recorder's windway & labium

The air jet coming out of the windway interacts with the air column in the instrument's bore and oscillates around the edge or labium, as shown in the pictures below. .


The interaction between the windway and the recorder's air column		The air jet oscillating around the edge of the labium. (Photos : Univesity of Eindhoven, Netherlands)

There is more information on the air jet in a text by A. Hirschberg (in Dutch) with a diagram & videos.

Click here for a close up view of the chamfers and the windway exit

THE RECORDER'S AIR COLUMN

The recorder's bore contains a column of air that vibrates lengthwise in the following manner when the instrument is blown into:
A velocity antinode (A), which is a zone with maximum movement and minimum pressure, forms at each end and a velocity node (N), a high pressure zone with no movement, forms in the middle.


A	N	A

Waves that travel along the bore of the instrument meet at the node and continue until they reach the opposite end of the tube where they bounce back, and keep on moving up and down in this way as long as the player keeps blowing.


A	N	A

The air column has several vibrating modes. These are called the registers and correspond to the partials (or harmonics) which are all present at the same time and give the instrument its tone colour.
The following graph reveals the sound spectrum of the 3rd fingering (low a) of a baroque alto or treble recoprder. It shows the frequency and amplitude of the different partials, each represented by one peak. The first one on the left is dominant. This is the note that we can hear. The others enrich it and caracterise its timbre.

sound spectrum for low a

We use the first four partials for playing notes over a range of two octaves. Below can be found individual information abour some of these notes. Click on the pictures below for more detailed information. The note names are for a baroque alto or treble recorder in f.

	low f (1^st register) (Click on the picture for more details)

The air column can be shortened by opening holes, giving higher notes, since the vibrating length is shortened. It can of course also be lengthened again by closing holes. If the holes were large enough, opening a hole would be equivalent to cutting the air column completely at that point, but the holes are too small for this, which is why we can use fork fingerings (also called cross fingerings) to play semitones in particular

	low a (1^st register) (Click on the picture for more details)

	low b (a fork fingering - 1^st register) (Click on the picture for more details)

	low d (1^st register) (Click on the picture for more details)

We can thus play over more than an octave up to g (a fork fingering on baroque type recorders)

	middle g (a fork fingering - 1^st register) (Click on the picture for more details)

Of course, we can also lengthen the air column again by closing the open holes.

To play higher notes we can inhibit the first register and force the air column to divide into two parts. On the recorder this is done by making the thumb hole leak. We now have two velocity nodes and each vibrating segment is shorter. This enables us to use the same holes again for other notes. We are now using the instrument's second register, for which the air column has two velocity nodes.

	middle a (2^nd register) (Click on the picture for more details)

By making two leaks (the thumb hole and one on the other side of the instrument), we can inhibit the first two registers and force the air column to divide into three parts, giving notes higher still, using the same holes once more. We are now using the instrument's third register, for which the air column has three velocity nodes.

	high e (3^rd register) (Click on the picture for more details)

By making three leaks (the thumb hole and two holes on the top of the instrument) we can inhibit the first three regkisters and force the air column to divide into four parts, giving even higher notes. We are now using the instrument's fourth register, for which the air column has four velocity nodes.

	high g (4^th register) (Click on the picture for more details)

In this way we can play over a range of two octaves and a half (about 30 notes) using only 8 holes. However, the design of the instrument must be correct to enable this.

The evolution of the recorder's bore profile over the centuries

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Philippe BOLTON,
22 Le Grand Portail, F-84570 VILLES-SUR-AUZON, France
TEL : +33 4 90 61 86 11