A rhythm game series by Creator/{{Harmonix}} that doesn't depend on special peripherals. All that's needed is a PS2 controller. Each song has 6 main tracks (drums, guitar, etc.). On each track, there are a bunch of gems representing that track's instrument. Hitting all the gems on a track for two measures activates that track temporarily. Your job is to move around the tracks and hit all the gems to keep them all activated.

The first game was Frequency, followed by a sequel, Amplitude, both on the PS2.

Made by Harmonix, who went on to make GuitarHero and RockBand.

!!The game provides examples of:

* AndYourRewardIsClothes: the various "arenas" in which the songs can be played, and the actual clothes for your Freq in Amplitude
* CompetitiveMultiplayer: And one of the first games to use the PS2's online network adapter.
* DifficultButAwesome: There isn't much better moments of euphoria than beating any of Frequency's harder songs on Expert mode.
* DigitalAvatar: The Freqs.
* InterfaceScrew: some of the powerups in multiplayer.
* LuckBasedMission: Getting [[GameplayGrading four bars]] on many Amplitude songs is a ''lot'' easier if the Freestyler power-up appears in the right places.
** Not quite luck-based. The power-ups appear in the same location every time the song is played, requiring players to [[TrialAndErrorGameplay discover the optimal path]].
* RhythmGame
* {{Techno}}: The majority of the music library, though some songs dip into the trance and [[ThrashMetal thrash metal]] territory.