a song is written in “one-one,” or even “one-two” (one or two notes more than an octave), but even such “rangey” songs make use of these notes only in the verses and confine the chorus to a single octave.  But in the end, the necessity for the composer’s writing his song within one octave to make an effective offering for his introducing singers, works out to his advantage.  The average voice of an octave range is that possessed by those who buy popular songs to sing at home.

Now here is a helpful hint and another bit of evidence from the music angle, to emphasize the necessity for the perfect fitting of words and music.  Let me state it as Berlin did, in an article written for the Green Book Magazine: 

3.  Melodies Should Go Up on Open Vowels

“Melodies should go up on open vowels in the lyrics—­A, I or O. E is half open and U is closed.  Going up on a closed vowel makes enunciation difficult.”

Experience is the only thing warranted to convince beyond doubt, so test this rule on your own piano.  Then take down the most popular songs you have in your collection and measure them by it.

4.  Put “Punch” in Music Wherever Possible

As we shall see later, another definition of the popular song-hit might be, “A song with a punch in the lyrics and a punch in the music.”  Berlin expressed the application to the problem of melody by the following: 

“In the ‘International Rag,’ for example, I got my punch by means of my melody.  I used the triplet, the freak, from out of my bag of tricks: 

Raggedy melody,
Full of originality.

5.  Punch is Sometimes Secured by Trick of Repetition

Anatol Friedland, who composed the music of “My Persian Rose,” and L. Wolfe Gilbert’s “My Little Dream Girl,” in discussing this question, said: 

“Ten notes may be the secret of a popular song success.  If I can make my listeners remember ten notes of a song that’s all I ask.  Whenever they hear these ten notes played they’ll say, ‘That’s. . .,’ and straightway they’ll begin to whistle it.  This is the music punch, and it depends on merit alone.  Now here’s one angle of the musical punch trick: 

“To make a punch more punchy still, we repeat it at least once, and sometimes oftener, in a song.  You may start your chorus with it, repeat it in the middle, or repeat it at the end.  Rarely is it repeated in the verse.  High-brow composers call it the theme.  For the popular song composer, it’s the punch.  Clever repetition that makes the strain return with delightful satisfaction, is one of the tricks of the trade—­as well as of the art of popular music.”

6.  A Musical Theme Might be Practically the Entire Song

If what Friedland says is so, and you may turn to your well-thumbed pile of music for confirmation, the theme or the punch of popular music may prove the entire song.  I mean, that in its final sales analysis, the magic bars are what count.  To carry this logical examination still further, it is possible for a popular song to be little more than theme.  As a musical theme is the underlying melody out of which the variations are formed, it is possible to repeat the theme so often that the entire song is little more than clever repetitions.