Will Smith, while a guest on The Tonight Show, teamed up with host Jimmy Fallon to create a beatbox-based hip-hop track, using only their voices and an iPad. The iPad app they used, called Loopy, takes individual recorded tracks and loops them over each other.
https://www.youtube.com/watch?feature=player_embedded&v=oazFK9awniE
No doubt Loopy has seen a rush of downloads since its appearance on The Tonight Show. It’s available for iPad and iPhone from the App Store.
Source: Kotaku
