Vicarious Visions is tasked with bringing Guitar Hero to the Nintendo DS and largely succeeds.
As you know, Guitar Hero: On Tour includes the game (on a standard DS cartridge), as well as an additional device that goes into the GBA slot. The fret bar device sports four familiar looking buttons and acts like the buttons on the guitar peripherals bundled with the console versions of Guitar Hero. The actual guitars usually have five buttons but the decision to include four here is wise considering that you don't want to be moving your fingers around while holding the DS. The actual fret bar is fairly comfortable to use, although it is possible to get hand cramps after extended sessions.
As expected, the gameplay formula of On Tour is similar to previous Guitar Hero games. You'll see notes going down the screen, which you'll have to hit in order to get a bonus multiplayer to score more points. You hold the buttons on the included device and strum by using the touch screen on the Nintendo DS. You can strum up and down, without having to lift up the stylus, which is very useful for faster paced songs. Familiar bits like Star Power are found in the game. The end result is that Vicarious Visions managed to translate the Guitar Hero formula remarkably well to the handheld.