<P> There are two types of MIDI controllers: performance controllers that generate notes and are used to perform music, and controllers that may not send notes, but transmit other types of real - time events . Many devices are some combination of the two types . </P> <P> Keyboards are by far the most common type of MIDI controller . MIDI was designed with keyboards in mind, and any controller that is not a keyboard is considered an "alternative" controller . This was seen as a limitation by composers who were not interested in keyboard - based music, but the standard proved flexible, and MIDI compatibility was introduced to other types of controllers, including guitars, stringed and wind instruments, drums and specialized and experimental controllers . Other controllers include drum controllers and wind controllers, which can emulate the playing of drum kit and wind instruments, respectively . </P> <P> Software synthesizers offer great power and versatility, but some players feel that division of attention between a MIDI keyboard and a computer keyboard and mouse robs some of the immediacy from the playing experience . Devices dedicated to real - time MIDI control provide an ergonomic benefit, and can provide a greater sense of connection with the instrument than an interface that is accessed through a mouse or a push - button digital menu . Controllers may be general - purpose devices that are designed to work with a variety of equipment, or they may be designed to work with a specific piece of software . Examples of the latter include Akai's APC40 controller for Ableton Live, and Korg's MS - 20ic controller that is a reproduction of their MS - 20 analog synthesizer . The MS - 20ic controller includes patch cables that can be used to control signal routing in their virtual reproduction of the MS - 20 synthesizer, and can also control third - party devices . </P> <P> A MIDI instrument contains ports to send and receive MIDI signals, a CPU to process those signals, an interface that allows user programming, audio circuitry to generate sound, and controllers . The operating system and factory sounds are often stored in a Read - only memory (ROM) unit . </P>

A midi port can connect musical instruments like an electronic keyboard to a sound card