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Re: [fluid-dev] New patch: polyphonic key pressure (aftertouch)

From: Aere Greenway
Subject: Re: [fluid-dev] New patch: polyphonic key pressure (aftertouch)
Date: Tue, 23 May 2017 08:47:53 -0600
User-agent: Mozilla/5.0 (X11; Linux i686; rv:45.0) Gecko/20100101 Thunderbird/45.8.0

On 05/23/2017 06:33 AM, Marcus Weseloh wrote:

2017-05-23 14:00 GMT+02:00 Kjetil Matheussen <address@hidden>:
So when fluidsynth receives these bytes:

0xa0 0x60 0x10
0x90 0x60 0x70

Is the note played with a volume value of 0x10?

That depends on the modulators on the instrument. Polyphonic aftertouch is not one of the standard modulators, so it needs to be explicitly added to an instrument / preset. On the standard FluidR3_GM font, your example would play with volume of 0x70, as there is no polyphonic aftertouch modulator on any of the presets.

If you add a Key Pressure -> Initial Attenuation modulator and leave the default Velocity -> Initial Attenuation modulator in place, then those two modulators will work in combination. So in that case: yes, sending aftertouch before note on will affect the initial volume of the sound. But it probably wouldn't be 0x10 in your example, because the velocity also adds to the volume through the default modulator.

By the way, that is (as far as I can tell) exactly the same behaviour as in the already implemented Channel Aftertouch event. Channel aftertouch is always accepted and stored on the channel, even if no note is currently playing and it is also not reset on note off. But Channel Pressure / Aftertouch _is_ one of the default modulators and is mapped to LFO Pitch Depth. So if we switch your example to Channel Pressure:

   Channel Pressure: 127
   Note On: 60 127

then that note starts with maximum volume and maximum LFO pitch depth.
In case, that doesn't seem right...

Ok... but what _is_ right? :-) And if that's not right, is the existing channel pressure also wrong?



fluid-dev mailing list

I have been using FluidSynth for years, by way of the Qsynth GUI interface, with a synthesizer having aftertouch (which it actually does by sending Channel Pressure MIDI control messages). 

It has always had the same effect as the modulation control message. 

With the FluidR3_GM soundfont (which comes with Qsynth as a dependency), the Modulation control often produces a non-pleasing sound, so I actually removed the Channel Pressure messages from my MIDI sequences. 

With other soundfonts, the Modulation messages (and therefore the Channel Pressure messages) are useful. 

It has had this behavior for over 10 years. 

Polyphonic Aftertouch may be different from Channel Pressure.  I am talking about Channel Pressure, which my synthesizer uses. 


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