                   THE WINDOWS MIDI MAPPER

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The MIDI mapper in Microsoft Windows allows you to customize
Windows to work with your particular MIDI hardware and software.
It functions much like the Windows printer and video drivers --
once they are correctly configured, you can use any Windows
program with these devices.

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SOME TERMS:
-----------

Channel
     Channels are used to separate songs to allow more than one
     instrument to sound at the same time.  There are 16 MIDI
     channels, and each channel can use a single instrument or
     patch at a time.

Patch
     Used to determine the sound to be used, such as piano,
     strings, or guitars.  Patches are used to select which
     instrument is used.

Velocity
     Velocity is a measure of how hard a note is pressed.  It
     specifies how loud the note is played.

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THE MIDI MAPPER
---------------

The MIDI Mapper remaps patches, notes, and channels, and adjusts
velocities.  It uses the Patch Map, Key Map and Setup to
determine how to do this.

Until recently, there wasn't any standard for patch or note
numbers.  Now there is the General MIDI specification, an
official specification published by the International MIDI
Association.  This standard does identify which instrument is to
be used for each patch number.  However, there are a large number
of MIDI sound files in circulation which do not follow the
General MIDI specification.  Playing these through a General MIDI
device can make them sound pretty bad.

-------------------------
MICROSOFT'S SPECIFICATION
-------------------------

Microsoft Corporation has produced their own version of the
General MIDI specification, complicating things somewhat.  The
Microsoft standards require less of the equipment than the
General MIDI standard.  General MIDI supports 32 notes sounding
at the same time on all 16 MIDI channels.  Microsoft has defined
two less capable devices -- a "basic" device and an "extended"
one.

Basic Device
------------

A Basic device must be capable of playing 6 notes, in at least 3
different instruments, as well as 5 percussion notes.  All sound
cards, including the original 8-bit sound cards, can do this. 
Basic devices play the melodic instruments on channels 13 through
15, with the drums on channel 16.

Extended Device
---------------

Extended devices must be capable of 16 melodic notes, using 9
instruments, plus 16 notes on 8 percussive instruments.  Extended
devices use channels 1 through 9 for melodic sounds, with the
drum track on channel 10.

Microsoft's Authoring Guidelines
--------------------------------

These guidelines provide for producing MIDI files that can play
on any system by putting 2 copies of the song in each file --
both a basic and an extended version.  Each must meet the rules
for its particular type, including placing the higher priority
sounds on lower numbered channels.

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WINDOWS MIDI DRIVERS
--------------------

To prepare for playing MIDI files under Windows, first install
the drivers that came with the sound card.  These are usually
installed automatically by the software setup program, or they
can be installed manually in the Control Panel.

Most sound cards also come with their own setups for the MIDI
Mapper.  These are typically labelled something like Basic,
Extended, and All.  The principal differences between them are
the channels used.  Note that for some cards the output for one
of the drivers will go to the FM Synthesizer (which is on the
sound card), while the output in another driver will go to the
external MIDI device.  If you are using only the sound card, you
will have to edit the maps to direct all of the output to the FM
Synthesizer.

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PLAYING THE G&S ARCHIVE MIDI FILES
----------------------------------

The All map is recommended for listening to the MIDI files in the
Gilbert and Sullivan Archive, and for listening to most
downloaded MIDI files.  This map listens to all 16 MIDI channels. 
This is important, as not all MIDI files follow either the
General MIDI or the Microsoft specifications.  The All map will
catch all of the instruments regardless of the combination of
channels used.

If you do not have a map that watches all 16 channels, create one
which sends the output of all channels to the FM Synthesizer.


                                     Gilbert and Sullivan Archive
                                                     July 4, 1995
                            http://diamond.idbsu.edu/gas/GaS.html
