Musical Sounds are produced by setting up vibrations in a string, a column of air, a skin, or solid matter.
STRING INSTRUMENTS or CHORDOPHONES:
String Instruments are bowed (eg violins), plucked (eg guitars) or struck (eg pianos). The pitch of the note produced depends upon the length, thickness, mass, and tension of the string. To sound a higher note one can decrease the length, thickness, or mass, or increase the tension — or alter all four. For example, the four strings of a violin are of the same length and at similar tension, but vary in thickness and mass. Each can thus be tuned to a different pitch. Higher notes can be played on each string by pressing it to the fingerboard, so leaving a shorter length free to vibrate.
WIND INSTRUMENTS or AEROPHONES:
Wind Instruments are played by blowing:
- across a hole on to a sharp edge (Flutes)
- between two flexible blades (Double Reeds such as oboes)
- between a flexible blade and a rigid mouthpiece (Single Reeds such as clarinets)
- past a flexible blade in a rigid slot (Free Reeds such as mouthorgans)
- between buzzing lips acting as reeds (Brass Instruments such as trumpets)
The first three types are known as Woodwind and the last as Brass. This distinction does not depend on the material from which the instrument is made, but only on the way in which it is blown. Though saxophones are made of brass, they are classed as Woodwind because they are played with a single reed, and although serpents and cornetts are usually made of wood, they are classed as Brass because they are played through buzzing lips.
The pitch of a wind instrument depends on its length and the shape of its bore. All use a series of partials based on the Harmonic Series, the Woodwind to a limited extent and the Brass extensively. These partials are present in varying strengths as upper partials in any note played on any instruments and are what give it its characteristic tone quality. On the note C the first sixteen are:
On a Brass Instrument these notes can be played by varying the tension of the lips and the air speed; on a Woodwind the first few can be played in the same way. On many modern Brass Instruments the notes between these partials are played by the use of valves, and on the trombone with a slide. In these ways extra length of tubing is added, thus lowering the pitch. On Woodwind Instruments, and some Brass, the scale starts on the lowest note of this series and holes are opened, one after the other, thus shortening the sounding length of the tube and so raising the pitch. When the top hole is reached, all are covered again, the player blows harder, producing the next partial, and opens the holes in sequence again.
Percussion Instruments are struck. They consist of either a skin stretched across a frame (Membranophones) or a shaped solid (Idiophones). Membranophones may have an open frame (frame drums, eg tambourine), another skin across the bottom of the frame (tubular drums, eg side drum), or have a closed body (kettle drums, eg timpani). The shape and material of the frame affects the tone; the diameter, thickness, mass, and tension of the skin controls the pitch. With Idiophones (eg xylophone, triangle, cymbal, etc) any shape and any resonant material can be used. The pitch depends on the nature, volume, density, rigidity, mass, size, and shape of the material.
Originally written in 1961
© Jeremy Montagu, 2017