In the music and production world a (hardware) controller is something we use as a human interface to other elements in a system. For example, a keyboard controller is used to play keyboard parts, where the performance data is transmitted to a device that produces the sound, whether it’s a rack mounted module, a software synth, or another keyboard. A control surface is conceptually a more generic form of controller. They come in many shapes and sizes with (in some cases) radically different capabilities, but the thing they have in common is that they are used to control the functions of some other device, often a computer software program. In our business the words “control surface” usually conjure up images of something looking like a mixing board. These aren’t actually mixing boards, but instead devices used to control other devices, which perform the functions of a mixing board (mixing, aux sends, panning, EQ, etc.). Now that so much production is done inside of computer software, it has become increasingly important to provide tools that enable musicians and engineers easy access to a familiar set of controls in order for them to most effectively be able to do their work. As such, control surfaces in many ways mimic the look and feel of a mixing board, even though in many cases they may provide more or different capabilities. Some control surfaces are designed specifically for a specific computer or software system, while others are more generic and may work with a variety of different systems. Nowadays many stand alone mixers are really nothing more than software based mixing boards under the control of a dedicated control surface, even though the outward appearance is that of a mixer. In some cases these mixers can also be used to control other software mixers.