Irving Berlin's "nine inviolable rules for writing a successful popular song" (c/o David Suisman, originally published in American Magazine in 1920):
1. The melody must musically be within the range of the average voice of the average public singer. . . .
2. The title, which must be simple and easily remembered, must be "planted" effectively in the song. It must be emphasized, accented again and again, throughout the verse and chorus. . . .
3. The ideas and the wording must be [appropriate for] either a male or a female singer . . . so that both sexes will want to buy and sing it. . . .
4. The song should contain heart interest [pathos], even if it is a comic song . . . .
5. The song must be original . . . . Success is not achieved . . . . by trying to imitate the general idea of the great song hit of the moment. . . .
6. Your lyric must have to do with ideas, emotions, or objects known to everyone . . . .
7. The lyric must be euphonious--written in easily singable words and phrases, in which there are many open vowels . . . .
8. Your song must be perfectly simple . . . .
9. The song writer must look upon his work as a business . . . .
And there you have it.