If a CCD camera was aimed at the keys of guitar hero then the places where the keys were pressed could give the output greater variety of form You could actually make music with it
One approach is have the guitar hero keys have multicolor cycling LEDS (visible or UV) such that the camera could
immediately tell which part of the key was pressed from the color changes
Also the camera could be mounted nearly "flush" with the guitar body at a narrow angle with just a millimeter or two active optical surface as the presence or absence of color at a particular micromoment would describe finger position
The RGB LEDs (link) cycles through hundreds of colors per second
regardless of optics the CCD detects a particular frequency of light at a particular moment The gradual shift of that frequencys strength communicates the amount of activity of the fingers Its a guitar hero that can be strummed
Now to make it niftier you could have two CCDs one that looked around like a regular webcam thus two or more persons guitar heroing around could automatically make a music video of their activities
There is even a chance that as Guitar hero is a synchronized activity it might be possible to teach simultaneous musical activity with the lights to make comusical activities easier "jamming' (wheny Katy presses green Lisa could also press green to create a pleasant combined sound)