[flocking] moog VCF filter.

Colin Clark colin at colinclark.org
Wed Jun 3 01:16:12 EDT 2015


Hi Derek,

I tried to find a good tutorial on what the Moog ladder filters do, but couldn't find much. I'm no analog synthesizer expert, but this unit generator in Flocking is a model of Bob Moog's original filter from the '60s. It's basically a low-pass filter where you can define the cutoff frequency and the resonance. Most filters tend to be pretty non-linear at their extremes, and it looks like you're modulating the cutoff of the filter (i.e. the frequency at which it attenuates the signal) very quickly. I'm assuming this, combined with your particular resonance values, is what's causing the sound.

I have it admit it's a pretty neat way to make nice percussion sounds.

Just to be sure there isn't a further bug, what's the "terrible sound" you hear? And what happens specifically when it occurs only after the sound playing for a minute?

Nice synth--it's really cool!

Colin

> On Jun 1, 2015, at 9:43 AM, derek riemer <Derek.Riemer at Colorado.EDU> wrote:
> 
> Hi,
> What does the MOOG VCF example do? I am curious, because by changing the example a bit as seen in this simple piece of code yields a pleasing kind of song that seems to even keep time. I am not really sure why this actually sounds good, because by changing some of the hardcoded constants it can make terrible sounds, or sometimes will play for a minute, and then start making terrible sounds.
> Thanks,
> Derek
> 
> 
> // A 24db low pass moog-style filter.
>             var synth = flock.synth({
>                 synthDef: {
>                     ugen: "flock.ugen.filter.moog",
>                     cutoff: {
>                         ugen: "flock.ugen.lfSaw",
>                         freq:2,
>                         //The magic constants. If I do some other values but this I get a terrible wooshing sound.
>                         mul: 5000,
>                         add: 7000,
>                     },
>                     resonance: {
>                         ugen: "flock.ugen.sin",
>                         freq:1/2,
>                         width:.25,
>                         mul: 2.5,
>                         add: 2.5
>                     },
>                     source: {
>                         ugen:"flock.ugen.saw",
>                         freq: {
>                             ugen: "flock.ugen.sequence",
>                             freq: 2,
>                             loop: 1,
>                             list: [220, 220 * 5/4, 220, 220 * 3/2, 220 * 4/3, 220*3/2, 220*2, 220*4/3, 220*5/4, 220*3/4, 220, 220*7/8, 256],
>                             options: {
>                                 interpolation: "linear"
>                             }
>                         }
>                     },
>                     mul: 0.5
>                 }
>             });
>                     
> -- 
> Derek Riemer
> 
> Department of Computer science Undergrad, proud CILA member, music lover, and much more.
> 
> "Selfishness is the black hole of the human soul: Give no light of your own, and eventually you are only darkness. Find where you shine & do." Doug Lee, @doug_lee42 on twitter.
> 
> email me at derek.riemer at colorado.edu <mailto:derek.riemer at colorado.edu> 
> Phone: (303) 906-2194
> 
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