Sound is perceptible activity of the all pervading life. Different sounds differ in their outer expression, but within it is one and the same activity which directs all sounds. It is in expression that sounds differ, because of the different instruments through which they are expressed. The deeper we penetrate into the mystery of sound, the more we are able to trace the link that connects all sounds. This link is what the musician calls harmony, and it is in harmony that is hidden the secret of joy and peace.