INTRODUCTION TO MIDI
MIDI, the Musical Instrument Digital
Interface, began as a serial interface bus
designed to connect electronic musical
instruments with each other and to
computers.
Now the term MIDI also refers to a file format
(usually with the .MID extension) that can be
used to store MIDI command codes as might
be found on a MIDI bus. These files can be
used to control a MIDI-compatible system
with synthesizers, samplers, and other MIDI
devices.
MIDI FILES
MIDI files support only instrumental music,
not vocals or nonmusical audio. MIDI provides
a powerful way to create and distribute
instrumental music on the Internet.
MIDIcompatible hardware and software are widely
available for creating music and MIDI files.
A major strength of MIDI files is their compact
size. A 20-minute of MIDI instrumental music
requires only 100KB of data compared to a 7.6minute of CD-quality audio that requires 80 MB
of disk space.
MIDI FILES
The secret of a MIDI file’s compactness is that
it contains no audio. Instead, it is a sequence of
commands containing instructions on how to
generate music. The commands in a midi file must
be interpreted by hardware or software that can
translate those commands into audio.
When you think of MIDI think of sheet electronic
music. For the music to be heard, the sheet
music’s directives must be played on one or more
musical instruments. The sheet music itself is not a
sound, just as a MIDI file is not audio.
PATCH
A patch is a setup that creates the characteristic
sounds of a musical instrument such as a piano or
guitar.
MIDI has 128 patch numbers or programs, which
are codes that identify musical instruments. A
patch map is a table used by a MIDI device to
determine which instrument sound is assigned to
which patch number. A patch map may assign
program 41 to a violin, for example, program 33 to
acoustic bass, and program 23 to a harmonica
GENERAL MIDI
A recommended specification for consumer
electronic MIDI instruments that includes a
uniform numbering of instrumental and drum
sounds.
One of the main problems that had caused
headaches for MIDI users, was the inconsistent way
that various instrument sounds were numerically
arranged between different brands of MIDI
synthesizers. Because of this inconsistency, it was
difficult to share MIDI song files with one another.
GENERAL MIDI
About twenty years ago, Roland Corporation
and Passport Designs spearheaded an effort
to establish a new minimum of “industry
standard” for MIDI instruments. The basic idea
was to create a universal, specific preset
instrument and drum setting that any
manufacturer could easily include within their
synthesizers. This new specification became
known as “General MIDI.”
FEATURES OF GENERAL MIDI
Here are the important “minimum features” that a General MIDI
compatible instrument will offer.
A standard set of 128 sounds to choose from when
composing musical soundtracks. The sounds are always
arranged in a specific numerical order from brand-to brand.
The capability of simultaneous playback of up to 16
separate instrument parts.
The technical term is
multitimbral – a GM instrument is, therefore, 16 part
Multitimbral.
A minimum of 64-voice playback. The technical term for
this is polyphony – a GM instrument has at least 64 Voice
Polyphony.
At least one Standard Drum Set or Kit. GM supports ten
drum sets or kits. The percussion sounds always have the
same note assignments from brand-to-brand.
FEATURES OF GENERAL MIDI
How do you tell if your instrument is General
MIDI compatible?
Look for one (or more) of the following logos,
either stamped or painted on the instruments itself.
GENERAL
MIDI
GS
XG
SYNTHESIZERS
A synthesizer is a piece of electronic
hardware (or equivalent software running on a
computer) that can combine and manipulate
multiple tones in complex ways to create
musical notes.
Some sound cards, such as some of the
SoundBlaster series from Creative Labs, have
basic built-in synthesis capability.
The terms multitimbral and polyphonic are
used to describe synthesizers.
SAMPLERS
A device that “records” short, sound
samples originally from real musical
instruments, singer’s voice or even a dog’s bark.
This unit also has a disk drive for loading and
saving sound samples. A front-panel interface
enables the user to edit samples.
When a sampler receives a MIDI command, it
executes it by playing one or more samples at a
pitch and duration defined by the command
MIDI SEQUENCERS
The sequencer is what plays the music. It
generates the commands sent to the
synthesizer and samplers to generate the
music (and the synthesizers and samplers
generate the audio).