> BTW : Julian Parker reverbs have been recently added in reverbs.lib Cool! I look forward to hearing the JPverb and Greyhole Reverbs.
It would be great if contributions on this level got an entry in demos.lib - Julius On Thu, Jun 10, 2021 at 2:00 AM Stéphane Letz <l...@grame.fr> wrote: > BTW : Julian Parker reverbs have been recently added in reverbs.lib > > https://github.com/grame-cncm/faustlibraries/blob/master/reverbs.lib#L541 > > https://github.com/grame-cncm/faustlibraries/blob/master/reverbs.lib#L573 > > https://github.com/grame-cncm/faustlibraries/blob/master/reverbs.lib#L597 > > Stéphane > > > Le 9 juin 2021 à 18:14, Gary Worsham <gary.wors...@gmail.com> a écrit : > > > > Thanks Julius! > > > > I also found a Faust definition of a stretched all pass in this reverb > published by Julian Parker in 2013. What's funny is that the stretched > allpass is defined but not used. I'll be giving it a whirl before too long. > > > > > https://github.com/supercollider/sc3-plugins/blob/main/source/DEINDUGens/faust_src/JPverbRaw.dsp > > > > By the way I made a VST and Windows standalone app from Julian's code: > > > > https://github.com/HolyCityAudio/Plugins/tree/main/ParkerReverb > > > > Thanks, > > > > GW > > > > On Wed, Jun 9, 2021 at 5:12 AM Julius Smith <julius.sm...@gmail.com> > wrote: > > > I think that most likely, Faust does not include a library function > which is a "stretched" allpass and a fixed delay line with an interpolating > allpass on the end doesn't quite give the same thing... does it? > > > > I think it does if you use an allpass-interpolating delay line, e.g., > > > > allpass_comb_stretched(maxN,N,aN,strf) = (+ <: > de.fdelay1a(maxN,N-1+strf),*(aN)) ~ *(-aN) : mem,_ : +; > > > > (compare to allpass_comb in filters.lib) > > > > Cheers, > > Julius > > > > On Thu, Jun 3, 2021 at 11:29 PM Julius Smith <julius.sm...@gmail.com> > wrote: > > Hi Gary, > > > > I had to google "stretched allpass filters" and found this: > > > > > https://dsp.stackexchange.com/questions/46221/real-time-implementation-of-cascaded-all-pass-filters-from-given-transfer-functi > > > > They appear to be a special case of what I normally would call "nested > allpass filters". In any case, Faust can certainly do this as well, and > it's a great opportunity for a recursive definition using pattern > matching. Take a look at allpassnt() in filters.lib for an example. (The > two-multiply lattice filter is a nested allpass.) > > > > Due to negative free time, I will keep a star on this in gmail and > circle back when I can, as I am definitely interested in this project. > Quick urgent questions always welcome, however. > > > > Cheers, > > Julius > > > > > > On Tue, Jun 1, 2021 at 7:22 AM Gary Worsham <gary.wors...@gmail.com> > wrote: > > Hi Julius, > > > > I made a brave attempt to read these articles. I only ever got as far > as EE263 and that was more than 40 years ago! Anyway, a few questions > regarding direct form biquad allpasses vs. "stretched" allpass blocks as > proposed by Julian Parker. > > > > I think that most likely, Faust does not include a library function > which is a "stretched" allpass and a fixed delay line with an interpolating > allpass on the end doesn't quite give the same thing... does it? > > I could probably take the Faust library definition of an interpolating > allpass and add the stretching internally. > > Only the stretched allpass blocks give that "imaging" effect where the > phase delay maximum is repeated up the spectrum, resulting in the need to > low pass filter to just keep the lowest one. However, now that I think of > it with another cup of coffee, even a single all-pass is going to have that > phase delay peak, meaning that above that transition frequency, the chirp > would go from high to low, while below it, it would go low to high. So you > still want to low pass filter the result so you only get the upward going > part of the chirp. > > Looks like calculating the coefficients for these filters requires > Matlab and Newton's method? eeek! That doesn't sound like something that > would be too easy to modulate in real time. > > > > Let me give a little more background on my actual goal here. A few > years ago I got pretty good at the Spin FV-1 and tried to drum up some > consulting business among guitar amp manufacturers. One of the amp > builders I talked to said "hey can you do that "Vinnie Bell" sound as > evidenced on the Ferrante and Teicher version of "Midnight Cowboy" and > "Airport Love Theme""? If nothing else, this stuff really has to take you > back! > > > > https://www.youtube.com/watch?v=payWL0Y8Dd4 > > https://www.youtube.com/watch?v=OsTne8nT8BI > > > > At first, listening, especially to the Airport one, I thought, well > that's a VCF with a really fast trigger going down and what we are hearing > is the upward sweep of the envelope decay - going into a short delay with a > little feedback. So I tried and tried to replicate that sound but I always > heard the initial sweep down. It's still a cool sound but it's not this. > So then I did my best to isolate some of the notes in Airport Love Theme > and generated a spectrogram using Audacity. That's when I saw the chirps. > Having read the Parker paper previously, but not having understood what his > images meant, it all suddenly made sense! They are about 50 msec apart, > there is no discernable sweep down at the beginning, and each successive > chirp per note is more and more flattened out. The transition frequency is > about 1750 Hz. As I understand it, that is VERY LOW for a typical spring > reverb. > > > > <image.png> > > > > I was talking to Jim Thomas, guitarist and composer for The Mermen, once > a few years back and played this sound for him, and he immediately said "oh > that's a spring reverb". I never got the sound with an FV-1 although I did > make some chirp blocks just to see what would happen. Exactly HOW Vinnie > Bell got this sound has been the subject of much debate since Vinnie > invented many of his own effects (and the electric sitar). Vinnie was > always reluctant to share his secrets and he passed away a couple years > back. Joe Gore concluded it was "really fast phasing" > https://tonefiend.com/live-looping/midnight-cowboy/ but I don't think the > spectrogram bears that out. I've wondered how he did it as well, > considering he was just one guy, not Bell Labs, working in the mid 60's. > So it probably WAS a spring reverb with just a single spring. As far as > how he got the transition frequency down to 1750 Hz, he either used a > custom spring, or (how's this for a wild guess) recorded it at 15 IPS and > played it back at 7.5 IPS? I mean, there's no evidence that this sound was > ever created live on stage anywhere. > > > > Phew! Sorry. So that's the kind of sound I am going for, and it being > really true to any real spring is not really a design goal. If anything I > would like to take that chirp into the outer limits by making it really > long, changing the transition frequency independent of the delay time (to > the extent possible), etc. It might also be interesting to see what > happens if you were to vary some of the aspects of the chip with the > guitar's envelope. > > > > Thanks, > > > > GW > > > > > > > > Virus-free. www.avast.com > > > > On Fri, May 28, 2021 at 9:10 PM Julius Smith <julius.sm...@gmail.com> > wrote: > > HI GW, > > > > I would use this method (simple fi.tf2() biquad allpasses in series): > > > > > https://www.researchgate.net/publication/224106863_Robust_Efficient_Design_of_Allpass_Filters_for_Dispersive_String_Sound_Synthesis > > > > @ARTICLE{AbelAndSmithDAFX06, > > AUTHOR = "Jonathan Abel and Julius O. " # Smith3, > > TITLE = "Robust Design of Very High-Order Allpass Dispersion > Filters", > > JOURNAL = dafx06, > > MONTH = sep, > > YEAR = 2006 > > } > > > > Cheers, > > - Julius > > > > > > On Fri, May 28, 2021 at 1:00 PM Gary Worsham <gary.wors...@gmail.com> > wrote: > > Sorry if this is a repeat but I've just signed up for the mailing list > again, and previous submissions said "you're not registered"... maybe I'm > in some sort of limbo at the moment. > > ================================= > > I'm interested in messing with some structures suggested by Julian > Parker's work on spring reverb emulation. > https://acris.aalto.fi/ws/portalfiles/portal/13004391/art_10.1155_2011_646134.pdf > > > > This paper suggests an "interpolating all-pass delay". Initially, I > don't think I would care about modulating these in real time, but of > course, everything is better with envelope modulation so I'd probably try > that eventually. > > > > The library includes a handful of all passes and of course I can try all > of them, but wondering if a particular one would be particularly swell for > this kind of thing. > > > > > https://faustcloud.grame.fr/doc/libraries/index.html#thiran-allpass-interpolation > > > > https://faustcloud.grame.fr/doc/libraries/index.html#fi.allpass_comb > > > > https://faustcloud.grame.fr/doc/libraries/index.html#fi.allpass_fcomb > > > > > https://faustcloud.grame.fr/doc/libraries/index.html#fi.allpass_fcomb5-and-fi.allpass_fcomb1a > > > > Note that I did some experiments in the past with this sort of thing on > a Spin FV-1 and found that chirp block lengths in the 12 to 20 samples > range (at 32768 Hz fs) seemed to work well for this sort of thing. > However, the FV-1 doesn't have enough instructions to generate a very long > chirp. I am really looking to emphasize the dispersion "chirp" in this > particular exercise. > > > > Thanks! > > > > GW > > > > Virus-free. www.avast.com > > _______________________________________________ > > Faudiostream-users mailing list > > Faudiostream-users@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/faudiostream-users > > > > > > -- > > "Anybody who knows all about nothing knows everything" -- Leonard > Susskind > > > > > > -- > > "Anybody who knows all about nothing knows everything" -- Leonard > Susskind > > > > > > -- > > "Anybody who knows all about nothing knows everything" -- Leonard > Susskind > > _______________________________________________ > > Faudiostream-users mailing list > > Faudiostream-users@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/faudiostream-users > > -- "Anybody who knows all about nothing knows everything" -- Leonard Susskind
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