Comment by criddell

I understand that being sharp or flat from a target note is called being off-key but I'm wondering where that came from? In my head, off-key would indicate that you are singing or playing a note that isn't the key of the piece (like A♯ if you are in the key of C).

I started thinking about this when trying to play along with stuff on YouTube and discovering that the entire song is sharp (likely sped up during mixing or mastering). Would you describe those songs as being off-key?