Ah, they DO have an entry in demos.lib, great! (My failed search was for "Parker")
On Thu, Jun 10, 2021 at 4:20 AM Julius Smith <julius.sm...@gmail.com> wrote: > > 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 > -- "Anybody who knows all about nothing knows everything" -- Leonard Susskind
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