MIDI and polyphony

Discussion in 'General Keyboard Discussion' started by dlesko, Oct 26, 2018.

  1. dlesko

    dlesko

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    Hi all. Got a question I can't seem to find the answer for. When a keyboard controller runs out of polyphony does it send a midi note off message to the VST for notes that it has to stop playing. IE, the controller has 32 note polyphony but you play 33 notes so it has to drop a note. Does that note cause the keyboard controller to send a note off message to the vst?

    Thanks in advance!

    -dlesko
     
    dlesko, Oct 26, 2018
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  2. dlesko

    SeaGtGruff I meant to play that note! Moderator

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    Keyboard controllers don't have polyphony, as that is a characteristic or function of sound modules. You can use a keyboard controller to play a sound module having a polyphony of 1 note-- such as a monophonic synth or soft synth-- and you'll be limited to playing one note at a time. You can then use that exact same keyboard controller to play a virtual instrument or hardware sound module having a polyphony of 256 notes and you'll be able to play up to 256 notes at the same time.

    When a hardware sound module, soft synth, or other sound source has a specific polyphony that's likely to be used up if you start layering voices together or using sustain to prolong notes long after you've released the keys, then it's up to the sound module to determine which notes will be cut off to free up tone generators for the new notes. As far as I know, it's standard practice for the oldest notes to be cut off.

    However, with monophonic synthesizers or monophonic patches it might depend on the notes themselves, sometimes with the user being able to select which "rule" to use, such as giving priority to the lowest note, to the highest note, or to the newest note. For instance, if you were to play three keys at once (i.e., a chord) then you'd actually get just one note, but it would either the lowest key or the highest key of the three, or if the last key pressed has priority then any one of the three keys might be the one whose note is played according to which of the three keys happened to get pressed last.

    EDIT -- As far as your question about "Note Off," the controller will send a "Note Off" when you release a key, not before, even if the sound module has to cut off the note early due to limited polyphony. Notice that there's not necessarily a direct correlation between when a "Note Off" event is received and when the corresponding note stops sounding, since a note can continue to sound after the key is released due to things like a long release time on the ADSR envelope, the use of a sustain pedal, an effect such as reverb or delay, etc. And conversely, a note can be cut off before the key is released due to things like a short sustain time and no release time on the ADSR envelope (such as a patch that's designed to play staccato notes no matter how long you hold the keys down), or the sound module cutting the note off so the tone generator that was sounding that particular note can be used to sound a newer note.

    EDIT #2 -- I mentioned effects such as reverb and delay, but those don't have a connection to the tone generators per se, since they're applied "after the fact" to the sounds produced by the tone generators. For instance, if you have a delay effect turned on that creates a lengthy echo which repeats many times as it gradually fades, the echoing note shouldn't continue to "tie up" one of the tone generators after the original note has ended, since the echoing delay effect isn't produced by the tone generator.
     
    Last edited: Oct 26, 2018
    SeaGtGruff, Oct 26, 2018
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  3. dlesko

    dlesko

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    ok got it. But what if your controller is also a digital piano on it's own? It's built in piano sounds have their own polyphony. Does that translate into midi data if also used as a controller?
     
    dlesko, Oct 26, 2018
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  4. dlesko

    John Garside

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    Usually, when a digital piano or sound module, etc., runs out of polyphony it releases the oldest played note.
    And then, no, the MIDI note off isn't transmitted until the note is actually released, even though the note has been replaced with another newer note ... generally speaking.
     
    John Garside, Oct 26, 2018
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  5. dlesko

    delaware dave

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    The piano sound itself is not sent via midi, just the depressed notes of the keybed and other controllers (pedals, knobs, sliders, etc.). If you were to play a controller that had built in sounds (ex. using a digital piano as a controller) you could set it up so that the piano comes out of the audio line out of the controller and midi out of that controller is connected to the midi in of a sound module, and that sound module is playing strings. You'd get the piano out of the line out of the controller and the strings sounds come from the audio line out of sound module that you are midi'ing to. If the sound module is 64 notes polyphony and the piano within the controller is 32 note polyphony, and you play 40 notes you will only hear 32 notes from the piano and all 40 notes from the strings. the 40 keys that you depressed on the keybed of the controller will all go through the midi out and trigger the sound module which can handle up to 64 keyed notes at one time, so you'll hear all 40 notes played through the sound module. The internal keyboard however can only play back 32 notes at a time so 32 notes will be heard and 8 will be lost. The piano sound itself is not transmitted out the midi line, only the keybed information, including sustain pedal, knob, slider info, etc..
     
    delaware dave, Oct 26, 2018
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