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.

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.

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!

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.