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Software 2000 Volume 1 (Disc 1 of 2).iso
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1987-08-15
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THIS FILE IS MADE AVAILABLE TO MIDI/WorldMusic, A ROUNDTABLE ON GEnie,
BY THE INTERNATIONAL MIDI ASSOCIATION (IMA), AND IS AVAILABLE FOR
DOWNLOAD BY PERMISSION OF THE INTERNATIONAL MIDI ASSOCIATION (IMA)
MIDI/WorldMusic IS ACCESSED VIA GENERAL ELECTRIC'S INFORMATION SERVICE,
GEnie. ONCE LOGGED ONTO GEnie TYPE "MIDI" OR "M430" TO MOVE TO
MIDI/WorldMusic.
TO SUBSCRIBE TO GEnie (300/1200/2400):
1. DIAL 1-800-638-8369
2. UPON CONNECTION, ENTER "HHH"
3. AT THE "U#=" PROMPT, ENTER "XJM11906,GENIE" AND RETURN
GEnie WILL STEP YOU THROUGH THE REST. IF YOU NEED FURTHER HELP CALL
1-800-638-9636.
TO SUBSCRIBE TO THE IMA CALL 1-213-649-6434. TELL THEM MIDI/WorldMusic
OF GEnie SENT YOU.
Perhaps the most confusing part of the MIDI specification (to
both experts and novices) deals with the four MIDI modes. In my four
years of being involved with the MIDI interface and attempting to
educate the public on its structure and uses I have come across every
possible misconception that I can think of regarding the four MIDI
modes of operation. Questions regarding modes pop up so often that I
have been able to define three basic points of confusion: names,
transmission v.s. reception and Mode 4 (Omni-Off/Mono).
Names
Most of the confusion here was caused by early misconceptions
by certain manufacturers implementing MIDI on their instruments. At the
dawn of the 'MIDI Era' there was a bit of confusions as to how modes
were implemented. In fact there were initially only three MIDI modes
defined in the MIDI specification previous to version 1.0. These three
modes were Omni, Poly and Mono. Omni and Poly were fairly straight
forward but the definition of Mono mode was interpreted incorrectly by
one prominent manufacturer. This caused an eleventh hour re-definition
of the structure of the MIDI modes as the specification was finalized
as version 1.0.
'Omni' is a condition that can be on or off and not a true MIDI
mode in and of itself. The condition 'Omni' is used in conjunction
with Mono or Poly modes of operation to define four individual MIDI
modes:
Mode # Omni
1 On Poly
2 On Mono
3 Off Poly
4 Off Mono
Unfortunately many people and some publications still refer to
the MIDI modes as Omni, Poly or Mono. As you can see this is not
always clear. Luckily, these three terms have come to represent three
of the four actual MIDI modes as follows:
Term True Mode
Omni Omni-On/Poly (Mode 1)
Poly Omni-Off/Poly (Mode 3)
Mono Omni-Off/Mono (Mode 4)
But what happened to Mode 2? Well, we like to call that the
'vestigial' mode. In other words its there but its really serves no
purpose. Mode 2 is defined as Omni-On/Mono. What this means is that
the synthesizer would attempt to respond to data coming down the MIDI
line on all channels, and then assign that data to a single synthesizer
voice - not the most practical of all applications.
So the end result is that there are four 'official' MIDI modes.
Only three of which are in common use and are refered to by the terms
'Omni', 'Poly' and 'Mono'.
Transmisstion/Reception
The next point of confusion is that of the difference between
the way modes operate with repsect to transmission and reception. Many
people mistakenly feel that MIDI modes are exclusively 'reception'
modes and have nothing to do with the way a synthesizer sends out data.
This is only partially correct. The condition 'Omni' is a reception
condition - where a synthesizer will respond to all messages regardless
of the channel number when Omni is 'on' and will respond only to data
matching its channel number when Omni is 'off'. Invariably the
question comes up on how to 'send data in Omni mode'. Well, MIDI just
doesn't work that way. What the questioner usually wants to know is how
to send data out through a MIDI system that will trigger all
synthesizers regardless of their mode or channel. In order to
accomplish this via transmission a synthesizer would have to
simultaneously send sixteen copies of each message triggered by its
keyboard or controllers. A large chord, some pitch bend and aftertouch
would easily tax MIDI's bandwidth and cause the log jamming of MIDI
data. This is clearly impractical and as such was not implemented in
the MIDI specification. When Omni is 'on' a synthesizer transmits data
on its basic channel only, even though is will respond to data on all
channels. In order to trigger all synths in a system it is necessary
to set the receiving instruments to 'Omni' mode or to the same channel.
So what do MIDI modes have to do with transmission? Mode 4
(Omni-Off/Mono) allows the synth to both send and receive data on
multiple MIDI channels. Most people are only familar with Mode 4 as a
reception mode where different parts can be played on a synth
multitimbrally, via separate MIDI channels (i.e. Casio's CZ-101).
However Mode 4 also allows for transmission on four MIDI channels.
Although few synthesizers, and only one sequencer that I know of,
implement this it is a very useful function. Specifically, a synth
sending in Mode 4 will send a polyphonic chord on multiple MIDI
channels. For example, assuming the basic channel of the instrument is
channel 1, a C major triad will be sent as C/channel 1, E/channel 2 and
G/channel 3 (note: the channels are selected according to the order in
which the notes are played and not their hierarchy within the chord).
Mode 4 v.s. Multi Mode
Now that we have gotten to Mode 4 we find ourselves at the
heart of yet another point of confusion about multi-timbral operation.
In the original MIDI spec the only type of multi-timbral operation
suggested was in Mode 4 which limits you to monophonic operation. As
synthesizer design advanced instruments were developed that could play
polyphonically on multiple MIDI channels. The Oberheim Xpander was one
of the first synths of this type. Specific zones and voices could be
'mapped' to ranges of the keyboard and/or MIDI channels. But what MIDI
mode is this? As it was multi-timbral it was typically called, albiet
incorectly, Mode 4.
This point was recently addressed by the MMA via a proposal
for a fifth MIDI mode - Multi Mode. After much discussion it was
decided that a synthesizer operating in Multi Mode was no different
from two or three synthesizers operating in 'Poly' mode, except for the
fact that it was a single instrument. A 16-voice synthesizer assigning
four notes each to four MIDI channels operates over MIDI identically to
four 4-voice synthesizers on separate MIDI channels. Because of this
it was decided to keep the four MIDI modes as they are and not to add
Multi Mode as a '5th mode'. However, it was decided that multi mode
would be a recommended way of identifying a synthesizer operating in a
multi-timbral/polyphonic mode.
End of list.
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