Hyperspeed is an unlockable cheat that, as the name suggests, increases the speed at which the notes move towards the strikeline. It has made an appearence throughout the entire series, and has become increasingly popular among highly skilled players.
There has been much debating amongst the Guitar Hero community regarding the cheat's legitimacy. As the notes increase in speed, they also spread further and further apart from each other, allowing players to better time the hits of individual notes and thus making for an easier experience. Supporters typically state that the increased speed only adds to the challenge, and that using speeds 3 - 5 can in fact make the game very difficult, thus requiring higher levels of skill to successfully use. Conversly, those who look down on its use state that using it on lower settings results in no negative effects. e.g. When used on speeds 1 - 3, the notes move slow enough that they can still be hit relatively easily, while still retaining the increased distance. Another common statement is that the setting is often put under a cheats menu, though this is often overlooked as irrelevant.
Other music games such as Dance Dance Revolution, beatmania, and Pump It Up have speed modifications which are part of regular gameplay with no codes needing to be input. In these games it is not considered cheating.
Scorehero does not consider hyperspeed cheating. However, Guinness World Records does not allow hyperspeed or any other cheats.
Hyperspeed appears in "Extras" section under "Options" in Guitar Hero 5 and Guitar Hero: Warriors of Rock.
From Guitar Hero III: Legends of Rock onwards, hyperspeed is available on 5 levels (as well as being off entirely), 1-5, 1 being the slowest scroll speed and 5 being the fastest. Each level increases the speed of the notes and fretboard by 40%. Level 5 will result in the notes moving twice as fast as they would without Hyperspeed.
Comparisons can also be made to the speed of the fretboard in multiplayer game modes such as Pro Face Off and Band play in Guitar Hero: World Tour onwards. It is generally considered that the hyperspeed level in single player is +3 the level it is on multiplayer, i.e. Hyperspeed 1 on multiplayer modes is the same as Hyperspeed 4 on single player modes. Proved Here