MIDI is the acronym for Musical Instrument Digital Interface. MIDI is a system very much like a player piano roll in that it is used to specify or control the actions of a synthesizer, virtual instrument, or other electronic and software devices, while the tone or effect is generated by the instrument or software itself. In other words, MIDI does not produce sound by itself.
The development of the MIDI system had been a major catalyst in the explosion of music technology in the latter part of the last century. MIDI put powerful computer instrument networks and software in the hands of less technically versed musicians and amateurs and provided new and time-saving tools for computer musicians. The system first appeared in 1982 following an agreement among manufacturers and developers of electronic musical instruments to include a common set of hardware connectors and digital codes in their instrument design. In 1983, the MIDI 1.0 Specification was formally released by the International MIDI Association* as Roland, Yamaha, Korg, Kawai and Sequential Circuits all came out with MIDI-capable instruments that year. Yet is it still in common use today, even being used with advanced synthesis software like MAX/MSP and Supercollider, theatrical lighting systems and show control, fireworks and Christmas light show synchronization, and a host of other applications not dreamed of when it was first proposed.
The original goal was to connect or interface instruments of different manufacture to control common functions, such as note events, timing events, pitch bends, pedal information, etc. A note, patch change or pedal applied to one instrument would have the same effect on another connected via MIDI cables, even if it was of a different brand. As small, affordable computers, such as the Apple II became available, it wasn't long before instruments were hooked up through a MIDI interface to the computer as well as each other. This allowed programmers to write MIDI sequencing and editor/librarian software.
Though several classes of codes have been added to the MIDI 1.0 Specification (International MIDI Association, 1989) and MIDI applications have grown far beyond the original intent, the basic protocol in use today has remained relatively unchanged. As of this writing, however, the MIDI 2.0 specification, the first major update in almost 40 years has just been released, though it has not yet been widely incorporated into instruments or software. The intent is, however, that it be backwards compatible with MIDI 1.0 devices and software. MIDI 2.0 utilizes two-way communication to determine the functionality of a device, auto-configure it to work together, or determine the device is only MIDI 1.0-capable and communicate on that level alone.
For comprehensive and updated information and new code changes, as well as information beyond the scope of this chapter, an excellent online source is MIDI.org. A free registration will provide access to many MIDI Manufacturer Association documents.
If you are unfamiliar with the binary and hexadecimal number format, before proceeding in this chapter, take a look at these three short tutorial pages from the next chapter. In addition, it may be helpful to print out this decimal/binary/hexadecimal conversion chart as you read through this chapter.
*According to Joel Chadabe, the International MIDI Association was formed to disseminate information and the MIDI Manufacturers' Association was formed to work on technical issues.