fluidsynth tremolo (modulation)

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fluidsynth tremolo (modulation)

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Hi

I am the author of eplayOrgan which uses fluid synth to produce its sound.
(Download it free from my website https://midimusic.github.io)

I am trying to implement tremolo (= midi modulation) and am using
fluid_synth_cc(synth, midichannel, 1, 100) to turn it on.
As far as I can tell this does not work, I get FLUID_OK returned but there is no modulation on the sound.

I am currently using fluidsynth version 1.1.8 on Windows.

Is this feature implemented for modulation?

If not how can I use fluidsynth to produce modulated notes in my organ. I know it can do it because qsynth provides modulation when driven by my midi keyboard and the "Modulation" wheel is advanced.

I have searched all the available documentation and your forum found nothing helpful.

Thank you
csw900 (David)




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Re: fluidsynth tremolo (modulation)

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The soundfont spec defines a default modulator for CC1. That means a value of 127 will result in a vibrato effect of +-50cents (not to be confused with tremolo).

This default modulator is implemented in fluidsynth, see this chart: https://github.com/FluidSynth/fluidsynth/wiki/FluidFeatures

I've just verified its correct behaviour using fluidsynth 2.1.3.

If the effect does not work for you, that default modulator may have been overridden by the soundfont you are using. It may also be that the delayVibLFO and freqVibLFO initial generators have been modified to cancel out any vibrato effect for whatever instrument you've tested with. You'll need to check that with a soundfont editor.


Tom




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Re: fluidsynth tremolo (modulation)

S. Christian Collins-2
You can set up a modulator in the SoundFont to route a MIDI CC to the
mod LFO volume, which will create a tremolo effect. However, as with the
vibrato, this effect is aligned independently with the start of each
note, which is not usually the effect you want for an organ, where a
single tremolo effect should modulate all notes simultaneously.

Have you considered adding a tremolo effect plugin to the audio chain
after FluidSynth?

-~Chris



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Re: fluidsynth tremolo (modulation)

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In reply to this post by fluid-dev mailing list
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 fluidsynth.

100 cents == 1 semitone

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


Tom





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