Frets on Fire is a program that can simulate the sound of a guitar with the keyboard, and is evidence that they advance a level, which requires some skill to go playing the notes that appear on screen. The goal is to play and learn.
It handles with F1-F5 (the guitar strings) for the left hand and the right to enter, but you can personalize, and even use the joystick. The tap on the correct notes increases the score and may compete with other players on the web. It is very similar to the game Guitar Hero (Plat Station 2) and allows you to import songs from it.
You will find several places to download songs for this game and in turn share their own.
Frets on Fire 1.3.110 is the latest version (November 2008) which is available for Windows, Linux and Mac, and is totally free .