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Re: [fluid-dev] fluidsynth tremolo (modulation)

From: Tom M.
Subject: Re: [fluid-dev] fluidsynth tremolo (modulation)
Date: Sat, 04 Jul 2020 14:51:23 +0200

David Back, 2. July 2020, 21:35:34 CEST dixit:
>  Thanks Tom
> Its a lot more complicated than I expected. I assumed that FS would use its 
> own implementation of CC 1 rather than using that of the sound font.
> It's encouraging to know that FS actually implements the function I am using 
> - I was very suspicious about this. The implementation may be only in version 
> 2 however - I am testing with version 1 at present and this does not work.
> The table says that FS uses the SF2 default MODULATOR yet you are talking 
> about VIB delay and freq !!!!! Which is correct? OR does it use BOTH? Please 
> let me know!
> The SF2 sound fonts I am using have both Mod & Vib defaults both have 8.2Hz 
> frequency, Pitch = 0, delay = .001
> The defaults are only overridden in SF2 instruments which have built in 
> tremolo. In this case both MOD AND VIB are used. Does FS use BOTH?
> I am an engineer not a musician and understand that "Vibrato" is frequency 
> modulation whereas "Modulation" is amplitude modulation. I am not too sure 
> whether organ tremolo is one or the other and its no good asking a musician 
> as they don't have a clue. In an organ it is produced by modulating the wind 
> pressure.
> I also do not really know what a "cent" is but assume that 50 cents = 1 
> semitone which would be enough for anybody and even less would be sufficient 
> for a tremolo effect.
> I can see that I will have to update to FS V2 which may cause other problems 
> in the eplayOrgan due to FS API changes.
> David

First of all, to make sure we speak the same language: The soundfont synthesis 
model uses the following nomenclature:

tremolo - A periodic change in amplitude of a sound, typically produced by 
applying a low frequency oscillator to the final volume amplifier.

vibrato - A periodic change in the pitch of a sound, typically produced by 
applying a low frequency oscillator to the oscillator pitch. 

...whereas modulation is just any kind of periodic change of any sound 
articulation, usually caused by modulators.

It is not clear to me what you are looking for. Fluidsynth will use whatever is 
written in your soundfont. If you use Mod and Vib, fluidsynth will use both. 
And if fluidsynth doesn't respond to CC1, the modulator was probably overridden 
in your soundfont. I'd need to look into the soundfont for any further help. 
The code you've sent me privately is not the problem. Neither is the version of 

100 cents == 1 semitone

Also, consider Christian's advice if you want to go for tremolo.


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