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. Download another file (Y/N)?