The EyeHarp is a digital instrument with a "gaze-controlled music interface" It helps physically disabled people learn and play music by syncing up with an eye-tracker (special camera) or any other device that controls a mouse pointer, like a mouse or a touchpad. Zacharias Vamvakousis's created the EyeHarp as his master and Ph.D. thesis at Pompeu Fabra University in Barcelona, Spain.
So how does it make music? According to a study, the Eyeharp allows users to "control pitch, timing and dynamics of a melody, as well as chords and arpeggios [notes of a chord played in succession] in a performance." The interface has two layers: the step sequence layer, and the melody layer. You create arpeggios in the step sequence layer, then control the chords to play melodies in the melody layer.