[Stk] [POSSIBLE VIRUS:###] Re: Wah-wah filter?

[Julius Smith]

Hey Perry,

It's great to see this wah pedal getting around.  I use it often and 
have been quite happy with it.  The only thing missing to my ears is 
the electronic noise and potentiometer scratchy sounds. :-)

- Julius

At 04:54 PM 10/6/2013, Perry Cook wrote:
>OK,
>
>Here's the ChucK project that implements and tests a simple
>2nd order resonator modeled after Julius' experimental CryBaby data.
>I use the ChucK ResonZ, because it takes .freq and .Q directly.
>It will take a touch more work to get that translated into parameters
>for the STK BiQuad or 2Pole, but totally doable.  Q is just Freq/BW,
>so with a little experimentation it should be easy to derive a radii[]
>array to use instead of the Qs[] array I use.
>
>(Gary/Others, maybe we should fold ChucK's ResonZ,
>BPF, HPF, and LPF back into STK???).
>
>Next i'm going to hook it to a MIDI pedal to control it.   Enjoy!!
>
>PRC
>
>
>
>
>
>On Oct 6, 2013, at 3:32 PM, Perry Cook wrote:
>
> > Of course!  I'll post in both ChucK and STK groups.
> >
> > PRC
> >
> > On Oct 6, 2013, at 3:31 PM, Robert Oschler wrote:
> >
> >> Hello Perry,
> >>
> >> Will you be posting the results?
> >>
> >> Robert
> >>
> >> On Sun, Oct 6, 2013 at 2:48 PM, Perry Cook <prc at cs.princeton.edu> wrote:
> >>> I especially like the end result of Julius' experiments
> >>> with his CryBaby:
> >>>
> >>> The estimated Q values printed at the end are
> >>> Q = [9.4, 4.0, 1.9],
> >>>
> >>> and the estimated pole frequencies are
> >>> fp = [464, 838, 2252] Hz.
> >>>
> >>> This, plus other data from that article, pretty much
> >>> sets you up to use a 2pole resonator, and just interpolate
> >>> between (and beyond) those values.
> >>>
> >>> Think ill code this up in ChucK this afternoon!!
> >>>
> >>> Prc
> >>>
> >>>
> >>> Sent from my iPad :-)
> >>>
> >>> On Oct 5, 2013, at 7:32 AM, Stephen Sinclair <sinclair at music.mcgill.ca>
> >>> wrote:
> >>>
> >>> On Sat, Oct 5, 2013 at 1:23 AM, Robert Oschler <robert.oschler at gmail.com>
> >>> wrote:
> >>>
> >>> Hello all,
> >>>
> >>>
> >>> I'm a veteran C++ programmer but I am brand new to the STK.  Although
> >>>
> >>> somewhat math challenged I do know basic DSP principles.  Is there a
> >>>
> >>> built-in effect that creates a good Wah-Wah pedal effect?  If so,
> >>>
> >>> where do I start poking around to use it?  If not, are there some
> >>>
> >>> low-level filter effects I can use to build one?  Or do I have to go
> >>>
> >>> it alone and create a separate block of code that does the DSP
> >>>
> >>> operations necessary to create the Wah effect?:  Note, need it to be
> >>>
> >>> fast enough for real-time processing.
> >>>
> >>>
> >>> http://en.wikipedia.org/wiki/Wah-wah_pedal
> >>>
> >>>
> >>> For the guitarists out there, I want to create a truly solid Wah
> >>>
> >>> effect that really sounds like a mouth opening and closing around the
> >>>
> >>> sound, something with some body to it, instead of an adjustable cutoff
> >>>
> >>> filter that sounds more like someone simply twisting the Treble knob
> >>>
> >>> on a stereo (is there some resonance processing involved with
> >>>
> >>> achieving an enhanced Wah effect?).  I'm going to use the effect to
> >>>
> >>> process the sound output of my current STK waveform output.
> >>>
> >>>
> >>>
> >>> Hi Robert,
> >>>
> >>> So there's a bit of work out there on wah wah pedal modeling if you
> >>> search google scholar.  One that jumps out is Julius Smith's work
> >>> which specifically shows how to emulate the Cry Baby pedal, perhaps
> >>> it's of interest:
> >>>
> >>> https://ccrma.stanford.edu/realsimple/faust_strings/faust_strings.pdf
> >>>
> >>> In general (if i understand correctly) a wah wah pedal *is* just a
> >>> resonant low pass filter.  You might be able to use STK's TwoPole
> >>> class to implement it.
> >>>
> >>> Not sure if that answers your question though, since I don't know
> >>> exactly what you mean by "something with some body to it."  (Not a
> >>> guitarist.)
> >>>
> >>> By the way if you just want some good guitar effects and don't want to
> >>> implement it yourself I suggest checking out Guitarix:
> >>> http://guitarix.sourceforge.net/
> >>>
> >>>
> >>> Steve
> >>>
> >>> _______________________________________________
> >>> Stk mailing list
> >>> Stk at ccrma.stanford.edu
> >>> http://ccrma-mail.stanford.edu/mailman/listinfo/stk
> >>
> >>
> >>
> >> --
> >> Thanks,
> >> Robert Oschler
> >> Twitter -> http://twitter.com/roschler
> >> http://www.RobotsRule.com/
> >> http://www.Robodance.com/
> >
> > _______________________________________________
> > Stk mailing list
> > Stk at ccrma.stanford.edu
> > http://ccrma-mail.stanford.edu/mailman/listinfo/stk
>
>
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Julius O. Smith III <jos at ccrma.stanford.edu>
Professor of Music and, by courtesy, Electrical Engineering
CCRMA, Stanford University
http://ccrma.stanford.edu/~jos/