Overstrumming is a term used to describe the occurrence of strumming notes that don't appear on the fretboard, i.e. playing notes that aren't there to play. Overstrumming can occur most often in extended strings of notes. When overstrumming happens, the game will notify the player of this in the same way it notifies the player that they missed a note, i.e. the game will make a "PLUNK!" or "WAIL!" sound.