Add
Private Notes
Music is one of the most familiar features of everyday life and in all cultures since time immemorial people have danced and sung in rituals, in celebrations, as an expression of joy, or just for fun.
Whenever the pressure of the air is changed rapidly, by beating a drum, by rattling a stick in a tin can, or by plucking a string stretched across a box, our ear-brain system detects the pressure changes as sound. The sound travels from the source to the listener as sound waves, but what are they really like? And why are some sounds musical and others just noise? The answer that we shall find for simple, single sounds is fairly easy: if the vibration is very regular the sound is more musical than if it is irregular. But, as soon as we move to the more complex sounds and mixtures that occur in the real world of music, the difference is far less easy to describe in any scientific way. The answer to the question of why some combinations of sounds seem more pleasant to the ear than others is not easy to find.
Some musical instruments (talking drums and trumpets of Africa) are used for sending information from one place to another. Is all music concerned with passing on information? Why do some people love a piece of music that other people hate? There are obvious differences in the musical likes and dislikes of people of different cultures and yet some people say that music is a universal language. How much of what we like is determined by our experience and upbringing and how much arises from the physics of the ear-brain system? What part does memory and conditioning play in our appreciation of music? Why do some sounds make us laugh and why can music have such a powerful effect on our moods?
It is unlikely that we shall find very clear cut answers to these questions, nor indeed to the general question posed by the title of this lecture. But we should have a good deal of fun exploring the subject with experiments and recordings and, hopefully, we shall know a lit
The origin of musical instruments is lost in the mists of time. It has been suggested that the strings developed from the twang of a bow string and the wind section seems very likely to have developed from the pan-pipes made with lengths of hollow reeds or from the sounds that can be produced by blowing into an animal horn. We shall be more concerned, however, with the essential features that have to be present in any instrument if a usable musical sound is to be produced.
The characteristic of a simple musical note is regularity of the pressure changes and the necessity for their frequency to be within the range to which human ears are sensitive. So we must obviously start with a device that will produce such regularity. It could be a vibration (or "wobble") or it could be rotation (like the wheel of a siren).
Most instruments depend on vibration of air in pipes, of tightly stretched strings, of more-or-less flat plates, or of hollow shapes like bells. So we shall need to start by thinking about how such things vibrate. And we shall have to consider how the vibrations are started and what effect this has on the notes. Pulling a cork out of a bottle makes a musical sound, but it is very short lived; how can we keep feeding in energy to make a continuous note?
Clearly plucking a guitar string, or striking a piano key make quite different sounds from those made by bowing a violin, even though the primary source is in each case a stretched string; so we shall ask how bowing can feed in energy to keep the sound going. Frequently we find that, even if we can keep it going, the sound is too quiet to be heard (a violin string without a body is almost inaudible).
So we need to amplify the sound and this can be done by adding a soundboard (e.g. in the piano), or a hollow body (e.g. in the acoustic guitar), or, in more recent times, by electronic means (e.g. in the electric guitar). But, as soon as we add an amplifier, complications arise. The amplifier does not
All stringed instruments start out with very quiet string vibrations that have to be amplified and we shall start by looking at the way in which flat plates and hollow bodies work in amplifying sounds.
Our exploration of real musical instruments will cover two quite different groups both of which use strings as their primary source of sound. The first group uses plucking as the way of setting the strings in vibration and includes all the fascinating instruments like lyres and lutes that have eventually led up to modern harps and guitars. Science has begun to contribute to our knowledge of the way in which guitars work and computer techniques are now being used to show visually exactly how the top plate of a guitar vibrates when a string is plucked.
The second group is one of the largest families of instruments, bowed strings, which derive from the quiet viols. Then came the baroque violins, cellos and other related instruments. But as orchestras became larger and the composers of symphonies and concertos demanded a more powerful sound, the baroque instruments were rebuilt to give our present day violins and cellos. Even the great instruments of Antonio Stradivari are no longer in their original form. And yet there is still a magic about them.
Can science help to reveal the secret of the "Strad"? How far can scientific methods complement the skill of the craftsman in making instruments? Among other, modern developments we shall see how the latest advances in laser interferometry can reveal not only how instruments behave, but how the body of the player is involved too.
Although we have mentioned only trumpets in the title this lecture is really about all the wind instruments, including the pipe organ. One of the main considerations will be the way in which the actual technology involved in making instruments has affected the whole course of musical development.
The early trumpets without valves could play tunes with only very high notes; the development of valves has, however, made it possible to play tunes at a much lower pitch. On the early woodwind instruments it was quite difficult to play very rapid passages but the introduction of Boehm's marvellous system of keys has made the instruments much more flexible. The opening clarinet glissando of the "Rhapsody in Blue" would be very difficult on a baroque instrument!
The simple ideas of vibrations in tubes soon have to be modified to explain the behaviour of real instruments and there are quite a few surprises. For example it is often said (frequently by the Lecturer!) that the trombone uses the various modes of vibration of the tube to produce the main pitch changes and then, in order to play tunes, the gaps are filled in by altering the overall length with the slide. But a good player can fill in the gaps without using the slide, apparently in defiance of the physics!
The design and manufacture of wind instruments is every bit as complicated as that of the string family. For example, in a clarinet the finger holes may seem to be there just to enable tunes to be played; but they perform a vital function in the maintenance of the vibrations, in determining the quality of sound produced and in controlling the way in which the sound produced inside the instrument gets out to the ears of the listeners.
The tone quality of the woodwinds makes a fascinating study and we shall find, for example that the note of a bassoon contains virtually no fundamental. The way in which the ear-brain system makes up for this loss is well worth studying.
The largest and most splendid of
Harpsichords and spinets are mechanised members of the plucked string family and it is well known that the major problem with these instruments is that it is difficult to make the sound vary in loudness.
In the harpsichord the problem is partly solved by having more than one keyboard, each playing an instrument of different loudness. But if, instead of using the keys to pluck a string, we use them to hit the string, some variation is possible, as in the clavichord. It is with the piano, however, that the full range of loudness is possible, and indeed the modern piano is a most extraordinary piece of mechanical engineering.
Any one learning to play a keyboard instrument has to practise scales and this is often regarded as the most boring part of the learning process. The origin of musical scales, however, is quite fascinating. They have often been likened to the grammar of music since they tend to emerge only after primitive compositions have been played or sung for a long time.
Our concern will be mainly with a problem that arises with all keyboard instruments - it is impossible to play scales in all the different keys exactly in tune and a compromise is needed. Fortunately the synthesizers that form the main material of this last lecture also provide us with convenient ways of demonstrating the problem and its solution.
The extraordinary world of synthesizers and computers has developed explosively in the last few years. One could call an electronic organ a synthesizer though of course it does not have the enormous flexibility of recent synthesizers.
Classification is difficult but broadly speaking one can trace a line of development from electronic organs to analogue synthesizers,because in both we start with purely electronic oscillations and then add, subtract, multiply, mix and perform many other functions to make up the complex sounds of useful music.
A second line of development involves digital processing in which even the basic sounds are
