The usual method is to take some theme that is filled with memories and make it over into a theme that is just enough like the familiar theme to be haunting.  This is the one secret or trick of the popular song trade that has been productive of more money than perhaps any other.

This lifting of themes is not plagiarism in the strict sense in which a solemn court of art-independence would judge it.  Of course it is well within that federal law which makes the copyrightable part of any piece of music as wide open as a barn door, for you know you can with “legal honesty” steal the heart of any song, if you are “clever” enough, and want it.  The average popular song writer who makes free use of another composer’s melody, doubtless would defend his act with the argument that he is not writing “serious music,” only melodies for the passing hour and therefore that he ought to be permitted the artistic license of weaving into his songs themes that are a part of the melodic life of the day. [1] But, although some song writers contend for the right of free use, they are usually the first to cry “stop thief” when another composer does the same thing to them.  However, dismissing the ethics of this matter, right here there lies a warning, not of art or of law, but for your own success.

[1] An interesting article discussing the harm such tactics have done the popular song business is to be found over the signature of Will Rossiter in the New York Star for March 1, 1913.

Never lift a theme of another popular song.  Never use a lifted theme of any song—­unless you can improve on it.  And even then never try to hide a theme in your melody as your own—­follow Mr. Berlin’s method, if you can, and weave it frankly into your music.

Now, to sum up all that has been said on the music of the popular song:  While it is an advantage for one man to write both the words and music of a song, it is not absolutely essential; what is essential is that the words and music fit each other so perfectly that the thought of one is inseparable from the other.  One octave is the range in which popular music should be written.  Melodies should go up on open vowels in the lyrics.  A “punch” should be put in the music wherever possible.  Punch is sometimes secured by the trick of repetition in the chorus, as well as at the beginning and end.  The theme may be and usually is the punch, but in the variations there may be punches not suggested by the theme.  Themes, semi-classical, or even operatic, or punches of old favorites may be used—­but not those of other popular songs—­and then it is best to use them frankly.

To state all this in one concise sentence permit me to hazard the following: 

The music-magic of the popular song lies in a catchy theme stated at, or close to, the very beginning, led into clever variations that round back at least once and maybe twice into the original theme, and finishing with the theme—­which was a punch of intrinsic merit, made stronger by a repetition that makes it positively haunting.