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.

After a successful Kickstarter campaign, a new [=HD=] Amplitude for the PS3 and PS4 with a new song list was released on January 5, 2016.

!!The games provide 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.
* ConceptAlbum: Amplitude 2016's campaign mode is one of these, based on reviving a woman in a coma using nanotechnology (that is, the Beat Blaster).
* ColorCodedForYourConvenience: Tracks in both versions of Amplitude are colored by their instrument..
* DifficultButAwesome: There isn't much better moments of euphoria than beating any of Frequency's harder songs on Expert mode.
* DigitalAvatar: The Freqs in the first two games, the different models of Nanoblasters in the 2016 game.
* HarderThanHard: In addition to the series' standard "Easy", "Normal", "Hard", and "Expert" modes, the 2016 ''Amplitude'' adds a "Super" difficulty after beating Expert, where there are no section breaks, you can't recover energy at all, and completed tracks regenerate faster.
* InterfaceScrew:
** Some of the powerups in multiplayer.
** In ''Amplitude'' 2016, the last main campaign mission causes a wavy multicolored effect at the last section. The final bonus song in the campaign has this effect for the entire length.
* NintendoHard: Given that the timing window is strictly hit-or-miss, the window for a hit is pretty small, especially in Frequency. If you're used to newer Harmonix games (or, worse yet, ''VideoGame/GuitarHero 3''+), or a newcomer to rhythm games, it can take some time to get used to. Compounded by the fact that [=TVs=] back then generally didn't have input lag...
* RankInflation: In Amplitude, your score at the end of a song is given a rating out of three bars, but the actual maximum you can get is four, or gold bars in ''Amplitude'' 2016.
* RhythmGame
* ScoringPoints: In Frequency and the first Amplitude, phrases have point values calculated by complexity of the note placement. In Amplitude 2016, phrase point values are simply the number of notes in the phrase.
* {{Techno}}: The majority of the music library, though some songs dip into the trance and [[ThrashMetal thrash metal]] territory.