Which Guitar Hero game was the first to feature drums and vocals?

Guitar Hero World Tour was the first Guitar Hero game to feature drums and vocals.

Earlier main Guitar Hero releases focused on simulated lead and bass guitar, using the familiar guitar-shaped controller and note highway. World Tour broadened the series into a full-band rhythm game by adding a drum kit controller and a USB microphone. Players could perform separate instrumental and vocal tracks together, making the game a direct response to the growing popularity of band-oriented music games such as Rock Band.

The distinction is about the Guitar Hero series itself. Guitar Hero 5 and Guitar Hero: Warriors of Rock also include drums and vocals, but they came later and therefore cannot be the first. Guitar Hero III likewise remained primarily a guitar-focused entry. World Tour also introduced tools for creating and sharing user-made music through its Music Studio and GHTunes features, so its importance was not limited to new peripherals: it helped redefine Guitar Hero as a broader virtual-band platform.