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.