[Stk] Wah-wah filter?

[Perry Cook]

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

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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/
> 
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