Let's put an end to all this bickering, shall we?
I have a wonderful music dictionary published by Harper Collins that gives a simply
beautiful definition of the word melody. It's rather lengthy, though, and I have no intention of typing it all out here. I did, however, find
another well written definition when I typed the words "music dictionary" into a search engine. Here's the link:
http://www.music.vt.edu/musicdictionary/
Regarding the original poster's
actual question about hooking a listener, I will say this: I believe there is no true formula for doing so. If there were, eveybody'd be doing it, right? Add to that the fact that what is "hooky" is largely subjective. For example, I personally have a difficult time picking out a hook in a semi-tone riddled piece of music from the Far East, while someone who is accustomed to listening to such a musical form would have a completely different perception.
That said, I can tell you what typically hooks
me, for whatever that might be worth to you. I always like to hear a composition that includes several distinct and unique parts contributing equally to the song as a whole. I'm often bored to tears when I hear two guitarists hammering out the same exact power chord riff while the bassist drones on the root note and the singer sings a "melody" that sounds strangely like the guitar line...
But then... I really like Black Sabbath, too, so...
Sometimes a solid unison part can be hooky, too, right? What the heck?
Again, it's largely subjective and there's no way to automatically hook everyone. Try hooking yourself first, and maybe it will be contagious!
Matt