As a project for CS890EH, Interactive Hardware, I am considering a project that would require a broad variety of hardware and software development: An optical synthesizer. Rather than producing sound, this synthesizer would produce light.
The signal would be initially produced in a similar fashion to a traditional analog synth, with a keyboard to set the fundamental frequency, and oscillators, filters, and envelope to modify the waveform. This waveform would then be fed to the Arduino, which using an FFT would isolate the frequencies into bins that would control the strength of a proportional frequency of light. This is not akin to a “visualization” as the system will not accept or produce any audible frequencies, and will be entirely built around the visual oriented objective.
The initial notes jotted above show a rough concept. The analog section would operate at frequencies in the KHz in order to stay above the audible range but remain low enough to keep the electronics simple. The arduino will then scale this input to the THz range of optical light, outputting to a variety of devices including an led grid or cube, possibly an RGB signal to a monitor, and most importantly to control some aspect of an experience in a Unity simulation.
John Desnoyers-Stewart's MFA Blog 