It is necessary to understand MIDI if you are interested in doing any creative
work with your soundcard.  


* WHAT IS MIDI?

It's a good bet that most of you have heard of MIDI by now.  For those that 
haven't, it's an acronym for Musical Instrument Digital Interface.  It's a 
standard method for electronic musical equipment to pass messages to each 
other.  These messages can be simple: 
        ("Hey, play a middle C until I tell you to stop") or complex: 
        ("adjust the VCA bias on oscillator 6 to match oscillator 1").

MIDI was developed in the early 80's and proceeded to completely change the 
musical instrument market and the course of pop music. Its growth exceeded 
the wildest dreams of its inventors and it is now firmly entrenched, to the 
point that you can't buy a professional electronic instrument that doesn't  
have MIDI.

Unless you were a musician, you might have ignored this startling growth.  
Now, the MIDI revolution has taken over the mainstream personal computing 
market.  The driving force is multimedia computing.


* WHY MIDI IS COOL

How does MIDI technology relate to multimedia?  You need to understand some of
the problems faced by multimedia producers to answer that one.  Every element
included in a multimedia presentation requires data storage and ultimately 
requires CPU and system bus attention from the computer to be played.

In the case of recorded digital audio, the data requirement can be staggering 
- up to 10 megabytes per minute for CD-quality stereo audio.  When you couple 
this with the requirement to be simultaneously playing other media, such as 
video animation or slideshows, it's easy to see how any computer can get
bogged down.

The main advantage of MIDI playback on the multimedia machine is its rather 
spartan data requirements.  One minute of rather busy music represented as
MIDI data only requires about 20 KB of data, 1/500th the size of CD quality 
digital audio!

Another advantage is that because the sounds being played are coming from a
synthesizer not a constant data stream from your hard drive, you can speed up 
or slow down the music without affecting the pitch.  This really helps when 
you need to time a piece of music to a specific timed event.

Yet another advantage is MIDI's total penetration of the music and lighting 
markets.  With MIDI, you can control such things as fog machines, light shows,
audio & video tape machines, CD players, audio effects, and even anything that
hooks up to AC power!  MIDI gives you the power to add all of these devices 
to your multimedia presentation.


* NO FREE LUNCH

As always, there are some "gotchas".  Not all MIDI synthesizers are the same.
Originally most multimedia soundcards used a synthesis technique called  
"FM Synthesis".  "FM Synthesis" has been replaced by "Wavetable synthesis".

Some companies (such as Turtle Beach) have moved more highly developed 
synthesis techniques from the electronic music market into multimedia with 
great success. Turtle Beach introduced Wavetable synthesis as far back as 1992
with its Multisound card (now called Multisound Classic) and has been
improving Wavetable synthesis ever since.

Wavetable synthesis uses digital audio recordings (samples) of real
instruments to re-create the exact instrument sounds.  The audio quality of 
systems that use "Wavetable synthesis" as opposed to "FM synthesis", is 
equivalent to a compact disc, so the music can sound just as good as any CD.

Although instruments and sound effects can be recreated with the use of 
synthesis, the human voice cannot.  This can be overcome by using a digitized 
audio recording of the voice section of a presentation while playing the MIDI 
sounds in synchronization; the lower the fidelity, the lower the data 
requirement.  Of course, you always have the option of talking above the music
in real time.


* MIDI BASICS

You can think of MIDI as an easily connected network between multiple devices 
(they don't even need to be computers or instruments!).  The most basic
function of MIDI is telling instruments what note to play.  The name of this 
command is a Note On.  

In this regard, MIDI is a lot like an electronic form of the old-style player 
pianos, where a hole punched in a sheet of paper forced a key down on the 
piano's keyboard.  MIDI performs the same task electronically.

The designers of MIDI had a good bit of forethought and made the standard 
extensible through the use of System Exclusive (SysEx) commands.  These
commands are sent with a special code at the beginning that is ignored by 
all but the desired receiver of the commands.

Since synthesizers have an ability to alter the sound of their musical output,
a command was included to instruct them to change their program, aptly called 
Program Change.               

There are many more messages in the MIDI standard, but these three are the
ones used by 99% of the applications of MIDI.  This brings us to the need for 
voicing standards and General MIDI.


* WHAT IS GENERAL MIDI?

As the MIDI revolution took over the professional music market, people began
to notice that it was very hard to exchange MIDI files and have them sound
right on any system but their own.  
The reason for this was simple:
     Most musicians had widely varying equipment, setups, and even preset 
     voices (if they had the same synthesizer).  There was no standard to 
     ensure that when I compose for "Grand Piano" on preset #12, your preset
     #12 had a grand piano sound on it. In fact, most of the time, the 
     resulting music was more like "staircase jazz" than anything else.

The International MIDI Association recognized the need for a standard set of 
voices that people could use to interchange MIDI files with and developed the
"General MIDI" or "GM" standard.  This standard enumerates 128 standard sounds
and their associated presets.  This means that when a composer uses a
honky-tonk piano sound in a General MIDI file, your sound card's MIDI synth
will play it back as a honky-tonk piano sound and not as a violin section.


* MIDI BUZZWORDS EXPLAINED
 
Like the computer industry, the music industry has developed many acronyms 
and buzzwords.  To the beginner in electronic music making, these can be 
intimidating.  We'll try to explain a few of the most common ones here.


* SYSEX

SysEx stands for System Exclusive, mentioned before.  System Exclusive is a
way for MIDI instruments to send hardware-specific commands.  SysEx messages 
can be used to save and load patch, keyboard, general and device-specific 
parameters.


* SEQUENCER

A sequencer is a software program that records and plays back the MIDI 
music data.  The basic analogy would be that a MIDI sequencer is like a tape 
recorder, except that it only records MIDI data.  Many sequencers exist for 
the PC, including Voyetra's Digital Orchestrator Pro and many more.

Most MIDI sequencer programs now allow you to record audio tracks in 
synchronization with MIDI tracks, allowing you to make complete productions 
including live voices and guitars playing along with MIDI drums, keyboards 
and orchestral sounds. Most film soundtracks and TV commercials are made this 
way nowadays, and some big name pop CDs too! 


* PRESETS

Each manufacturer tends to define the voice architecture of their synthesizer 
using different terms for marketing reasons, but in general terms every 
synthesizer has a number of easily available sounds that it can be called on 
to produce.  These are commonly called presets or patches.  

Most PC based synthesizers offer only the basic 128 General MIDI presets 
required by the MPC-2 specification.  The Turtle Beach Cancun offers over 300 
sounds and 15 drumsets in the Roland GS format, which includes all the General
MIDI sounds with over 200 more. 


* VELOCITY SENSITIVITY

The designers of MIDI knew that simply turning a note on and off wouldn't be
expressive enough to make realistic sounding music so they invented a method 
of including the strength of a note along with the note's play command.  
This is called velocity. 

Most soundcards can be programmed to use the velocity information supplied by 
the sequencer or MIDI keyboard to do many things, like to blend between two 
different wavetables, bend pitch, filter sound, etc.  Velocity variations add 
a lot of life to MIDI music that can otherwise be dull and flat sounding.


* MODULATION

Original analog synthesizers were basically sine wave generators that were 
controlled by a computer or musical keyboard.  The pioneers of electronic 
music swiftly determined that by varying the pitch of an oscillator, a much 
more convincing synthesizer tone could be created.  This effect when applied 
to pitch gives the subtle tremolo of a concert cellist or a contralto opera 
singer.  Modern synthesizers allow incredible versatility in modulating 
different sound sources with sine, ramp, and even random waveforms.


* RECORDING AND PLAYING MIDI 

A commonly asked question is how to set up a Windows session with a sequencer.
In a normal sequencing environment, you want the MIDI OUT of your keyboard 
controller to go to your soundcard's MIDI IN. You should then choose your 
soundcard's External MIDI IN as the MIDI input port in your sequencer
software.  

Your synthesizer, whether it is built into your soundcard or is built into 
your keyboard, needs to receive the MIDI data coming out from your sequencer
program.  If you want to use an external synthesizer for playback, choose the
External MIDI Port (often identified as "MPU-401") as the MIDI Out port in
your sequencer program's MIDI device setup.  If you want to use the built in 
synthesizer on your soundcard, choose the soundcard's Internal MIDI Synth 
(the name will be different for each soundcard).


Polyphony: 
----------
    How many sounding keys that can be depressed at a given moment without
    layering voices.  This is not to be confused with sounds or patches.


Voices:
-------
    A MIDI patch or sound is made up of a certain number of voices or layers
    for example a Piano patch may need 5 voices to produce the complex Piano
    sound. 


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