MSG as the Hook: An essential ingredient for a full-flavored song.
There's a reason you like Chinese take-out so much. After all, you've made meat and vegetable stir fy on your own plenty of times, but never crave that nearly as much. Why? MSG. It's an addictive chemical additive. And it makes you want to use your chopsticks again the next day.
Great songs all do that same thing - addict you. It's the hook that gets stuck in your head. It helps you learn the song, and feel like you know the song. And therefore, you want to hear it again.
There's probably no better master of the hook than the Fab 4. And it's not just a melodic lyric. You can hook with a guitar riff. You can hook with alliteration. And they did all of it - in just about every song, including "Paperback Writer" embedded above.
Lesson for the day: Don't forget the hook. If it's not getting stuck in your head, it won't get stuck in theirs.