MIDI (pronounced "mid-e") is a technology that
makes creating, playing, or just learning about music easier and
Playing a musical instrument can provide a lifetime of
enjoyment and friendship. Whether your goal is to play in a band,
or you just want to perform privately in your home, or you want to
develop your skills as a music composer or arranger, MIDI can
How Does MIDI Work?
There are many different kinds of devices that use MIDI, from
cell phones to music keyboards to personal computers. The one
thing all MIDI devices have in common is that they speak the
"language" of MIDI. This language describes the process of playing
music in much the same manner as sheet music: there are MIDI
Messages that describe what notes are to be played and for how
long, as well as the tempo, which instruments are to be played,
and at what relative volumes.
Because MIDI data is only performance instructions and not a
digital version of a sound recording, it is actually possible to
change the performance, whether that means changing just one note
played incorrectly, or changing all of them to perform the song in
an entirely new key or at a different tempo, or on different
MIDI data can be transmitted electronically between
MIDI-compatible musical instruments, or stored in a Standard MIDI
File for later playback. In either case, the resulting performance
will depend on how the receiving device interprets the performance
instructions, just as it would in the case of a human performer
reading sheet music. The ability to fix, change, add, remove,
speed up or slow down any part of a musical performance is exactly
why MIDI is so valuable for creating, playing and learning about
Three Kinds of MIDI
The original Musical Instrument Digital Interface (MIDI) specification defined a physical connector and message format for connecting devices and controlling them in "real time". A few years later Standard MIDI Files were developed as a storage format so performance information could be recalled at a later date. The three parts of MIDI are often just referred to as "MIDI ", even though they are distinctly different parts with different characteristics.
The MIDI Messages specification (or "MIDI Protocol") is probably the most important part of MIDI. Though originally intended just for use with the MIDI DIN transport (see Part 2) as a means to connect two keyboards, MIDI messages are now used inside computers and cell phones to generate music, and transported over any number of professional and consumer interfaces (USB, FireWire, etc.) to a wide variety of MIDI-equipped devices. There are different message groups for different applications, only some of which are we able to explain here.
There are also many different Cables & Connectors that are used to transport MIDI data between devices. The "MIDI DIN" transport causes a lot of confusion because it has specific characteristics which some people associate as characteristics of "MIDI" -- forgetting that the MIDI-DIN characteristics go away when using MIDI over other transports (and inside a computer). With computers a High Speed Serial, USB or FireWire connection is more common. Each transport has its own performance characteristics which might make some difference in specific applications, but in general the transport is the least important part of MIDI, as long as it allows you to connect all the devices you want use!
The final part of MIDI are the Standard MIDI Files (and variants), which
are used to distribute music playable on MIDI players of both the hardware and software variety. All popular computer platforms can play MIDI files (*.mid) and there are thousands of web sites offering files for sale or even for free. Anyone can make a MIDI file using commercial (or free) software that is readily available, and many people do, with a wide variety of results. Whether or not you like a specific MIDI file can depend on how well it was created, and how accurately your synthesizer plays the file... not all synthesizers are the same, and unless yours is similar to that of the file composer, what you hear may not be at all what he or she intended.
Even More MIDI
Over the past 20 years MMA member companies have created many
extensions and enhancements to MIDI that are designed to address some of the issues mentioned briefly above.
General MIDI (GM) and Downloadable Sounds (DLS) help address the issue of predictable playback from MIDI
Files. Scalable Polyphony MIDI helped bring MIDI to mobile
phones by providing a standard means for scaling playback of
complex MIDI files across a variety of low-power handsets. More information
on extensions and enhancements are available throughout this web
site, especially in the TechSpecs
Many people today see MIDI as a way to accomplish something,
rather than as a protocol, cable, or file format. For example,
many musicians will say they "use MIDI", "compose
in MIDI" or "create MIDI parts", which means they
are sequencing MIDI events for playback via a synthesizer, rather
than recording the audio that the synthesizer creates.