The Poetic Idea of the Piece
"Despite the popular impression that music is imitative in the sense of being able to reproduce different pictures and different emotions, it is really very far from it. The subject of program music and illustrative music is one of the widest in the art, and at the same time one of the least definite. Except in cases like the Beethoven Pastoral Symphony, where the composer has made obvious attempts to suggest rural scenes, composers do not as a rule try to make either aquarelles or cycloramas with their music. They write music for what it is worth as music, not as scenery. Very often the public or some wily publisher applies the title, as in the case of the Moonlight Sonata or some of the Mendelssohn Songs Without Words. Of course there are some notable exceptions, and many teachers may be right in trying to stimulate the sluggish imaginations of some pupils with fanciful stories. However, when there is a certain design in a piece which lends itself to the suggestion of a certain idea, as does, for instance, the Liszt-Wagner Spinning Song from the Flying Dutchman, it is interesting to work with a specific picture in view—but never forgetting the real beauty of the piece purely as a beautiful piece of music.
"Some pieces with special titles are notoriously misnamed and carry no possible means of definitely intimating what the composer intended. Even some forms are misleading in their names. The Scherzos of Chopin are often very remote from the playful significance of the word—a significance which is beautifully preserved in the Scherzos of Mendelssohn.