Answer: I think the principles of melody are really the same in all genres. The principles are simple - they are discussed with examples in Exploring Theory with Practica Musica , but they can be boiled down to just a few ideas: successful melodies move mostly by step, with some leaps. Large leaps tend to be compensated (usually moving immediately by step in the opposite direction from the leap). When there are several successive leaps they normally outline a triad. You might be able to say, though, that the notes of successful pop melodies are particularly likely to stick closely to the notes of a single scale. I can still remember how pleased I was in high school when I suddenly realized that most of the pop tunes I knew could be played on just the white keys of a piano. At the time, that seemed like a revelation.

Most people, male or female, are most comfortable singing within about an octave plus a fourth, maybe a fifth. Voices vary, of course, but for someone like me that would be maybe the G at the bottom of the bass clef up to middle C or D. And perhaps that is why so many well-known tunes hardly get outside a single octave; I think people tend to enjoy tunes they can either sing themselves or at least imagine singing. Serious singers, of course, can go much farther, and if you're talking about men singing falsetto that's an octave higher, in the same range as women. It's worth remembering that men reading a melody in the treble clef will generally be singing an octave lower, whether they know it or not, so you can just write your tune in the treble clef and try to avoid going much above the C above middle C.