Comment by dsign

I don't understand either what, technically, "off-key" means. I mean, sure, in well-known songs the singer needs to sing certain parts at a certain pitch, and it sounds awful when they don't. But say this is a song you are composing. There, you have your chord progression, but the chords and their notes are some sort of guidance. You may compose the song in such a way that the singer sticks strictly to the notes in the chord as much as possible, but that sounds weird and requires no small amount of singing skill. Or you may keep the singer a perfect fourth or a minor third away from some notes of the chord for part of the melody, "off key", and it may still sound good.