Singing slightly off-note. When this happens in published work (e.g. YouTube videos, CD's, etc.) most of the audience doesn't even notice, but people with a strong sense of pitch (most notably, perfect pitch) can easily notice this.
"Mark made such an awesome cover, don't you agree?"
"What do you mean? He was singing flat the entire song."
"What do you mean? He was singing flat the entire song."
by Gazotey September 10, 2017