This is more than an air guitar - it's a fire guitar and it's the most dangerous, but most impressive, Arduino project we have encountered to date.
There have been fire organs before. All you have to do is set up some burners and modulate the gas flow in sync with the music and the result is impressive.
However, the FireHero project is altogether more impressive. It uses a complex propane system and some electric valves coupled to an Arduino controller that hooks directly into a "guitar" - a Guitar Hero input device, hence the name of the entire project "FireHero". The result is that the notes played directly affect the flames.
Just watch and you will have to agree that it's impressive:
You can find out how it was built on Chris Marion's website, and a lot of the detail is in constructing the burners. The first attempt to connect the Guitar Hero controller involved wiring directly to the switches inside, but this was changed to direct decoding of the serial output of the device - an old PS1 was used to provide the necessary connector.
The Arduino accepts the inputs and controls the gas valves using some high voltage relays. The program is written in Processing.
The Guitar Hero interfacing code was created by another Arduino enthusiast, Bill Porter. Inspired by FireHero he is working on a color version of the musical flame thrower called ColorHero - you can see an early demo in the video:
It looks as if fire is going to be this year's top Arduino interface.