Beethoven was deaf when he composed his greatest works; with this EEG system by Eduardo Miranda of the Interdisciplinary Centre for Computer Music Research at the University of Plymouth, the next great composer could be a paralyzed person who has no formal training as a musician.
Miranda's EEG system teaches "composers" to focus on the same stimulus and use their minds to focus on a task -- pushing a button, for example. Those brain signals become associated with that activity; when the brain detects these patterns, the device creates a musical note. The intensity of the note can also be varied by the brainwaves.
The video above, with Beethoven playing in the background, illustrates how looking at an image can create electronic music.