I have gone through different phases in my music writing. There was a time when I used a little exercise — incorporating all of the twelve notes in the chromatic scale — to get me going. I used this technique for a while, but I don't any longer because I am going back to simpler melodies. Originally I moved away from the simple songs because I thought they were too simple.
"Songwriting" in Making Music (1983) edited by George Martin, p. 70