Amplitude is a rhythm game developed by Harmonix Music Systems and released for PlayStation 2 in 2003, serving as the direct sequel to their 2001 title Frequency. Players navigate across multiple instrument tracks within each song — such as guitar, bass, and drums — activating note sequences to build up the full musical composition. Successfully completing a track locks it in and frees the player to move on to another instrument lane, creating a dynamic back-and-forth across the musical arrangement. The core structure carries forward the multi-track gameplay established in Frequency while refining and expanding on its predecessor's approach. The game features a licensed soundtrack spanning multiple genres, and its mechanics laid important groundwork for the music rhythm genre that Harmonix would continue to develop in subsequent titles.
In Amplitude, the player controls a ship (referred to as a "Beat Blaster") moving down a path of varying shapes and lengths, containing up to six tracks. Each color-coded track corresponds to a different aspect of the song, such as percussion, synth, bass, or vocals, and contains a sequence of notes. As the player hits buttons corresponding to the note placement on the track, the notes activate a small portion of the track. If the player successfully activates enough notes in sequence, the track is "captured" and the section will play automatically for a number of bars, freeing the player to capture another section. The object of the game is to capture a sufficient amount of sections to reach the end of the song. If the player continually misses notes, an energy meter empties until the game is over.
