MIDI became the industry standard in 1982 and is maintained in the United States by the MIDI Manufacturers Association. Since then, MIDI has become an integral part of music production and performance, especially for genres such as pop, hip-hop and electronica.
Most audio production software uses the MIDI format, which can be used to make beats, compose bass lines and orchestrate a string section, among other things. Even without special software, almost all computers understand MIDI and can play back .midi files.
The MIDI parameters contain information such as note value, duration and velocity (volume) instead of actual sound. This enables a keyboard part to be input directly into a computer and then edited note by note.
Even though they understand MIDI, computers usually do not come with a built-in MIDI-port, which allows an external keyboard or other instrument to communicate directly with the computer, so a sound card will be needed. However, many keyboard controllers come with a cable that enables transfer of MIDI information through a USB port.
MIDI is often used in performance situations to enable a keyboard to control other sound modules, greatly expanding the palette of available sounds.
Another popular use of MIDI is stage lighting--the MIDI data can be used to automatically cue lights in time with the music.