The first indispensable requirement of music is a series of notes which stand in some recognisable relation to one another in respect of pitch; for there is nothing which the mind can lay hold of and retain in a succession of sounds if the relations in which they stand to one another are not appreciably definite. People who live in countries where an established scale is perpetually being instilled into every one's ears from the cradle till the grave, can hardly bring themselves to realise the state of things which prevailed before any scales were invented at all. And the familiar habit of average humanity of thinking that what they are accustomed to is the only thing that can be right, has commonly led people to think that what is called the modern European scale is the only proper and natural one. But it is quite certain that human creatures did exist for a very long time without the advantage of a scale of any sort; and that they did have to begin building up the first indispensable necessity of musical art, by deciding on a couple of notes or so which seemed satisfactory or attractive when heard one after the other; and that they did have to be satisfied with a scale of the most limited description for a very long period.