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pantherb / setBfree

DSP tonewheel organ
http://setbfree.org
GNU General Public License v2.0
194 stars 35 forks source link

Swell Pedal not emulated. #92

Open FalconBry opened 10 months ago

FalconBry commented 10 months ago

First of all, thank you for these great sounding emulations!

I noticed however that the Swell Pedal function on the organ is not fully emulated. On the actual Hammond organs the swell pedal has a variable filter function as well and does not mute the audio on minimal pedal setting. Any ideas on this?

Thank you.

x42 commented 10 months ago

No immediate thoughts on this.

Various other aspects are also not completely or correctly modeled. e.g. Key-click: the actual switch closes each of the 9 harmonics incrementally, rather than all at once..

FalconBry commented 10 months ago

Hi, thank you for answering.

Do you know what kind of filtering is used in the original? I don't have the schematics, but I read somewhere that it gradually cuts mids when the pedal goes back. Kind of variable loudness filter. Either-way it shouldn't be to hard to implement some variable IIR filter in the swell gain stage. Just need to know specs of the filter circuit.

As for the 9 pole mechanical key switches; also the harmonics will not all switch on at the exact same time, right? Just how audible these things are I don't know. The swell pedal filtering however is very noticeable since it not only alters volume but tone also.

On another note; I have been trying to change the mic distances and mic angles but did not notice any audible difference. Is it perhaps not implemented yet?

Thank you for your time!

x42 commented 10 months ago

Someone was already working on that (based off a paper https://pubs.aip.org/asa/jasa/article/142/5/2808/685076/Dynamic-temporal-behaviour-of-the-keyboard-action). I just mentioned it as example that the lack of proper emulation does not really impact the realism.

x42 commented 10 months ago

I have been trying to change the mic distances and mic angles but did not notice any audible difference.

It is subtle, and easier to discern in the standalone leslie plugin.

FalconBry commented 10 months ago

I agree. Certain aspects are not worth emulating properly. But as mentioned, the swell pedal is IMO. It's a huge part of the hammond organ playing style. I'll see if I can find out more about the B3 swell circuitry frequency response and translate that into an IIR filter.

Thanks for the link. Interesting reading!

x42 commented 10 months ago

It won't be a trivial change, but to get started search for swellPedalGain in src/tonegen.c

FalconBry commented 10 months ago

Yes, I know. In the mixdown section of oscGenerateFragment(). I have already fixed the zipper noise on the swell pedal there. Will try to inject an IIR filter there too.

helander commented 2 months ago

I have problem with the mentioned zipper noise, anyone that could assist?