As a part of the December 8 update to Rock Band 4, the game's most adept and hardcore players will get a new challenge that requires their finely honed skill set. Harmonix is introducing Brutal Mode to the game, a variation on standard Rock Band gameplay where it gets tougher the better you perform.
In Brutal Mode, notes disappear as they float down the path. But, it's still on you to play them in time, even though they're invisible when they eventually reach the bottom. There's an invisible barrier tied to the crowd meter that determines when the notes disappear. If you're playing really well, you might only get to see notes for a fraction of a second; if you're on the cusp of failing, they're stay visible almost until it's time to play them.
While it's still four days from release, Brutal Mode seems like a way to place more emphasis on the songs in Rock Band. It'll require less visual coordination, and instead rely on feeling the music, so to speak.
Brutal Mode is a challenge only for the most dedicated Rock Band players. The tracks can't be played on anything less than expert difficulty, and the entire band has to be playing the mode at the same time. In the event that a song is cleared, crimson stars are awarded -- a blood-red monument to the blood, sweat, and tears you put into besting Rock Band 4's toughest challenge yet.
See Rock Band 4's Punishing New 'Brutal Mode' - IGN First [IGN]