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.

Overstrumming can also occur when a guitar hero guitar controller strums multiple times after only being strummed once by the player. Also known as Multi-strumming, double strumming, triple strumming, or nubstrutting; (A derogatory term for the tactic used by newer players that modify their controllers in order to multi-strum faster songs without much effort.) This controller glitch can be fixed, according to some reports, by using a rubber band on a certain part of the guitar controller.