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PostPosted: Wed Mar 07, 2007 5:07 pm 
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Mr. Electonica Dude
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Joined: Wed Jul 14, 2004 1:48 am
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Location: Godly Taxas
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Machine type: AW4416
In the beginning is Midi , most sound generators were able to send and receive on one single midi channel only . They were also unable to generate more than one sound at once . (sound = one note played) This meant that if you composed a song requiring several different patches i.e.. piano , bass and drums on a sequencer you needed several tone modules to accomplish this. Each patch required a dedicated sound generator ! A rather expensive proposition for most players.

Today most sound generators are multitimbral. A multitimbral module can produce several (usually up to 16) different sounds at once. Each sound is accessed via a separate midi channel. Now it is possible to make sophophisticated arrangements on one tone module with several patches at once.

The number of sounds that can be produced simultaneously and addressed separately via midi depends on the model of the tone module.

It is quite common for beginners is to confuse the terms multitimbral and polyphony. Let's go ahead and clear this up while we are here. X-part multitimbral means that the generator is able to produce X amount of sounds simultaneously, On the other side of the rock , X-voice polyphony simply means that it is not able to play no MORE than X notes at once.

An example is on order here to understand this important concept. Say your device offers 16 part multitimbral. This means that you can access up to 16 sounds at the same time via midi. However you have only one voice (note) available for each sound. For most of us it's not possible to use one sound for several different notes so chord placing is not an option.

Things are not so bleak on the real world as manufacturers have come up with a couple of ways around this problem. Modern sound generators do not assign voices statically as in the above example. Voices are assigned dynamically. Dynamic voice assignment means the available voices are assigned to sounds on demand. Sounds complicated but here's an example.

Imagine a sequencer that addresses 3 sounds of a 16 voice module. A bass , a piano and a string patch. The song we are working on requires the bass to use 2 voices (notes at once) the piano 6 , and the strings 10.
If the voices were assigned statically then we would be 2 voices (notes) short. That means if the sequence (or manual playing) calls for more than 16 notes , then the first one played is going to get "dropped" and the newer note will sound. My Dave Smith evolver is 4 part multitimbral with four notes polyphony.

The device operating dynamically , constantly monitors the sounds to check how many voices are needed at any one given point in the sequence (song) . These voices are then assigned upon demand. So in a nutshell as long as song never uses more than 16 notes at the same time then there will not be any "dropped" notes upon playback.

Nowadays manufacturers are taking another approach to "polyphony versus mutitimbral" Today very affordable devices with 64 to 128 voices (notes at once are not uncommon.) Both my Yamaha ES and Triton are 16 are voice multitimbral and 128 note polyphonic in the "Voice Mode"
In the "Performance Mode" up to four multitimbral voices can be assigned to each midi channel (that's a whopping 64 separate voices at once folks) and the 128 note polyphonic note limit is still is effect. Yamaha has allowed this to be increased by adding certain plug in boards for more voices as well as polyphony. In the analog synth world Dave Smith has allowed one to increase the 4 note polyphony limit by adding the rack mount Poly-Evolver (for a total of 8 notes) or (a single mono-evolver (for 5 total.) Each add on unit increases polyphony from 4 or 1 note respectively.

Y'all still with me? (We'll eventually get to the G's midi functions)

Next.........How to make music with MIDI

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Good judgment comes from experience, and a lot of that comes from bad judgment.


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