Have you ever noticed?

I nearly always have music running through my head. However, I have just recently noticed that I actually only "hear" the melody - there isn't any harmony. Try it for yourself; pick a song or hymn you know really well, that has harmony that you also know really well - try O Sacred Head - and run through the music in your head. If you're like me, you actually only "hear" the melody, and you can only hear the harmony at places where the note is held so you can switch to hearing another part. Isn't that interesting?