Songs are divided into two general classes: those expressing the relationships of human beings, such as love, joy, sorrow, chivalry, patriotism, etc., and those expressing the relationship of man to his creator; veneration, devotion, praise, etc. The two great sources of inspiration to song writers have always been love and religion.
What are the principles of song construction? They are all comprised in the law of fitness. The composer must do what he sets out to do. The materials with which he has to work are rhythm, melody and harmony. The most important thing in a song is the melody. This determines to a very great extent the health and longevity of the song. Most of the songs that have passed the century mark and still live do so by reason of their melody. There must be a sense of fitness between the poem and the melody. A poem which expresses a simple sentiment requires a simple melody. A simple story should be told simply. If the poem is sad, joyous, or tragic the melody must correspond. Otherwise the family discords begin at once. Poetry cannot adapt itself to music, because its mood is already established. It is the business of the composer to create music which will supplement the poem. A lullaby should not have a martial melody, neither should an exhortation to lofty patriotism be given a melody which induces somnolence.
The same sense of fitness must obtain in the accompaniment. The office of the accompaniment is not merely to keep the singer on the pitch. It must help to tell the story by strengthening the mood of the poem. It must not be trivial or insincere, neither must it overwhelm and thus draw the attention of the listeners to itself and away from the singer.
The accompaniment is the clothing, or dress, of the melody. Melodies, like people, should be well dressed but not over dressed. Some melodies, like some people, look better in plain clothes than in a fancy costume. Other melodies appear to advantage in a rich costume. Modern songwriters are much inclined to overdress their melodies to the extent that the accompaniment forces itself upon the attention to the exclusion of the melody. Such writing is as incongruous as putting on a dress suit to go to a fire.