In Rise of the Tomb Raider, Crystal Dynamics used, for the first time, procedurally generated music: the percussion music during combat scenes is composed and played by a software system in real time. It never loops, adapts dynamically to game action, and is different with every gameplay. Furthermore, the music is based on the game composer's original music: his original MIDI scores and sample data are analyzed in order to compose new music in his style during the game. In this talk, one of the game's audio designers discusses in detail the the benefits of procedurally generated music, as well as the issues and limitations faced when working with it. Videos from the game will be used as illustration.