I started designing front panels for a modular synthesizer I was building, and inadvertently started an international business.
My design goal for these has always been to expose the module's functionality in the clearest, simplest way.
The most famous musician (that I know of) using instruments I designed is Martin Gore, of the British synthpop band Depeche Mode.
This is a photo of Gore's studio in Santa Barbara, highlighting four of my modules.