In Metal: Hellsinger, Death Is Your Instrument

gamespot.com:

First-person shooter combat can often be said to have a sort of «rhythm,» with the explosive bassy blasts of rounds leaving firearms and the weighty ka-chunk of reloading adding its own percussion to action movie-like experiences. Metal: Hellsinger makes that idea its central tenet, specifically building a fast-paced arena shooter around rhythm game sensibilities. But while it might seem like shooters naturally lend themselves to a rhythm game concept, making Metal: Hellsinger work as one, while ensuring it's still a satisfying shooter, meant that developer The Outsiders had to allow the music to permeate every facet of the game's design.

Just ahead of Summer Game Fest, The Outsiders released a free demo for Metal: Hellsinger on Steam that offers a look at one level of the game, as well as a boss fight. Playing as a demon called The Unknown, you shoot your way through the hordes of hell with a variety of weapons; the demo includes a shotgun and a pair of revolvers, as well as a sword and a flaming skull that spits fireballs. The better you keep the beat with your attacks, the higher your score multiplier rises; with it, the music playing in the game's level becomes fuller and more intense, and even the environment reacts to your slayage. Maintaining the beat keeps your multiplier up, while certain actions, such as reloading, reward you for your syncopation by getting you back to the battle faster. And at least one action, a brutal execution move that rewards you with a spray of health items, can only be performed if you activate it on-beat.

At Summer Game Fest, combat designer Adam Wrange explained what The Outsiders has had to do to keep time throughout Metal: Hellsinger, joking that he's had to add studying music