I'm working on a simple light show sort of thing for a guitarist friend. Aside from preset knobs, I'm trying to think of simple ways for him to interact with the device to trigger modification. First thought was sound input, I just want a very vague sense of decibels, could this be done with just a piezo buzzer? Another idea was using an LDR for foot control but I don't know what the light conditions will be, is there some other way to get a virtual wah pedal type input without getting really complicated? Any and all other ideas on hands free input would be very appreciated.