Re: Attenuation of Volume by use of Frequency Cutoff Parameter

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Re: Attenuation of Volume by use of Frequency Cutoff Parameter

jbeach2646
I have discovered a measured attenuation of the volume of a sample  wave file when using the frequency of the concert pitch of a note as the frequency cut-off value, that is to say,
when using 261 as the frequency cutoff parameter value for Midi Note 60, Middle C, measured volume is -26.6.  When frequency cut-off is not used, (that is, it is left open to the maximum of 20,000 Hz,  the measured volume is –10.8.
I recorded the same note, with, and without, a frequency cutoff parameter equal to the concert pitch of the note, playing a note of an instrument on the virtual keyboard in Polyphone, recording the output directly to Audacity.  Using the Effects>Contrast feature in Audacity, the measured difference in the volumes of the two recorded wave samples was –15.8.  
 
The use of frequency cutoff reduces the unrealistic shrillness of synthesized sound, making it more pleasant to hear, and, IMHO,  emulative of pipe sound.  What I did not realize was the
extent to which attenuation occurs as a side effect of frequency cutoff.  This is a problem, since, in the particular case of strings, while their shrillness is reduced, their volume is attenuated to an unacceptable degree.
 
I have brought up the subject of the 4 concomitant elements of the jOrgan or Fluidsynth Reverberation, Room (Space), Width (Size), Damping (absorption, perhaps) and Level (theoretically, the fullness of effect of the settings of Room, Width and Damping), and how any single increment of any one of their individual, slider or counter settings affects the quality of the whole.  It is difficult to describe for purposes of accuracy, but I find it frustrating to realize that the interrelationships between settings, varying one element more or less than another can produce the same relative reverberation quality, making it problematic to assign fixed values which are meaningful to other members of the forum.   The fact is that all of these factors affect the realism of the quality of the sound output, to say nothing of treble and bass settings in the properties of the soundcard devices.  
 
Any comments or suggestions would be appreciated.   Again, it is that old “standardization” thing for the purpose of relative meaning in the context of the group. 
 
I never dealt well with abstracts or abstractions and somewhat resent the concept that they defy delineation for accuracy of description.  That is, somewhat, comparable to what reverberation
is as an acoustic factor impacting the quality of sound, particularly, as regards virtual or digital sound.
 
John Beach 

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Re: Attenuation of Volume by use of Frequency Cutoff Parameter

lwalls
The most effective way that I have found to use the "frequency cutoff" MIDI controller
(CC 74) is for emulating the opening and closing of a pipe organ's swell shades.

To do this, simply add an MPL line for each swell shoe/pedal element such that as the
value of the expression control (CC 11) increases, make the value of the Frequency Cutoff
controller (CC 74) decrease INVERSELY.  You will have to play with the multiplier
value and the base-line constant to get the proper degree of cutoff at various volume
levels.  Trial and error adjustment of these constants will get you to a fairly
reasonable emulation of pipe organ swell shades.

CC 74 gives a decent approximation of the affect that opening and closing swell shades has
on perceived frequencies.  It is obvious that the closing of the swell shades reduces
the perceived volume level.  And that is exactly what CC 11  (or CC 7) does.  But CC 11
alone does not produce the same increasing "muffling" effect on higher frequencies that
real swell shade closure produces.

So, as the volume level is reduced with CC 11, you should INCREASE the high frequency
"muffling" effect by adding a CC 74 controller that increases in value, i.e., highest
volume level == least frequency attenuation, and vice versa.

Before spending a lot of time configuring CC 74 in your jOrgan disposition, make sure
that your sound source (Fluidsynth, LinuxSampler, hardware synth, etc.) actually
supports the CC 74 controller.

Since most jOrgan users probably use the built-in Fluidsynth sound source, it is
important to check this out.  I don't use Fluidsynth (I use LinuxSampler), so I
have not personally confirmed that Fluidsynth supports CC 74.

Maybe someone this list has already confirmed this.

CLW
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On 4/6/2018 1:09 PM, John Beach wrote:

> I have discovered a measured attenuation of the volume of a sample wave file when using
> the frequency of the concert pitch of a note as the frequency cut-off value, that is to say,
> when using 261 as the frequency cutoff parameter value for Midi Note 60, Middle C,
> measured volume is -26.6.  When frequency cut-off is not used, (that is, it is left open
> to the maximum of 20,000 Hz,  the measured volume is –10.8.
> I recorded the same note, with, and without, a frequency cutoff parameter equal to the
> concert pitch of the note, playing a note of an instrument on the virtual keyboard in
> Polyphone, recording the output directly to Audacity. Using the Effects>Contrast feature
> in Audacity, the measured difference in the volumes of the two recorded wave samples was
> –15.8.
> The use of frequency cutoff reduces the unrealistic shrillness of synthesized sound,
> making it more pleasant to hear, and, IMHO,  emulative of pipe sound.  What I did not
> realize was the
> extent to which attenuation occurs as a side effect of frequency cutoff.  This is a
> problem, since, in the particular case of strings, while their shrillness is reduced,
> their volume is attenuated to an unacceptable degree.

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Re: Attenuation of Volume by use of Frequency Cutoff Parameter

lwalls
Try...

Engaging set 176, set 11, set value | mult 0.5 | add 0.5 | mult 127
Engaging set 176, set 74, set value | mult -1 | add 1 | mult "x" | add "y" | mult 127

where  0 <= "x" <= 1, and 0 <= "y" <= 1, and "x" + "y" = 1.

(Note that it is the "| mult -1 | add 1 |" arithmetic that makes the inverse computation.)

Experiment with different values of "x" and "y".

Increasing "x" towards 1.0 and decreasing "y" towards 0 INCREASES the high freq.
filtering effect.  It should be most noticeable at LOWEST volume, and least
noticeable at full volume.  That's the swell shade closure "muffling" effect that we're
trying to achieve here.

If you can't hear any effect, even with x=1 and y=0, then maybe Fluidsynth simply
does NOT support cc 74 at all.

Lynn
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On 4/7/2018 9:16 AM, John Beach wrote:

> Anyway, can you give an example of what the MPL for the CC74 would be if the Swell
> Expression MPL is:  Engaging set 176, set 11, set value |mult 0.5 | add 0.5 | mult volume 127
> Intercept  equal 176, equal 16, set value | mult 100
>
> I have tried the following:  Engaging  set 176, set 74, set value | div 0.5 | sub 0.5 with
> the above Swell expression MPL and it makes no audible difference, having no effect.

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