Metris is a version of the Tetris game that uses a player’s musical response to control game performance. The game is driven by two factors: traditional game design and the player’s individual sense of music and sound. Metris uses tuning principles to determine relationships between pitch and the timbre of the sounds produced. These relationships are represented as bells synchronised with significant events in the game. Key elements of the game design control a musical environment based on just intonation tuning. This presents a scenario where the game design is enhanced by a user's sense of sound and music. Conventional art music is subverted by responses to simple design elements in a popular game.