1
2declare name "karplusplus -- Karplus-Strong + Fuzz";
3declare author "Yann Orlarey, Albert Graef";
4declare version "1.0";
5
6import("music.lib");
7
8// control variables
9
10// master volume and pan
11vol	= hslider("vol", 0.3, 0, 10, 0.01);	// %
12pan	= hslider("pan", 0.5, 0, 1, 0.01);	// %
13
14// excitator and resonator parameters
15size	= hslider("samples", 512, 1, 1024, 1);	// #samples
16dtime	= hslider("decay time", 4, 0, 10, 0.01);// -60db decay time
17
18// fuzz parameters
19drive	= hslider("drive", 0, 0, 50, 0.1);	// overdrive factor
20res	= hslider("res", 0, 0, 20, 0.1);	// filter resonance
21tone	= hslider("tone", 20, 1, 20, 0.1);	// filter cutoff harmonic
22level	= hslider("level", 1, 0, 10, 0.01);	// output gain (%)
23
24// voice parameters
25freq	= nentry("freq", 440, 20, 20000, 1);	// Hz
26gain	= nentry("gain", 1, 0, 10, 0.01);	// %
27gate	= button("gate");			// 0/1
28
29/* The excitator: */
30
31upfront(x) 	= (x-x') > 0.0;
32decay(n,x)	= x - (x>0)/n;
33release(n)	= + ~ decay(n);
34trigger(n) 	= upfront : release(n) : >(0.0) : +(leak);
35leak		= 1.0/65536.0; // avoid denormals on Pentium
36excitator	= trigger(size);
37
38/* The resonator: */
39
40average(x)	= (x+x')/2;
41att(d,t)	= 1-1/pow(db2linear(60), d/(SR*t));
42comb(d,a)	= (+ : fdelay(4096, d-1.5)) ~ (average : *(1.0-a));
43resonator(d)	= comb(d,att(d,dtime));
44
45/* DC blocker (see http://ccrma.stanford.edu/~jos/filters/DC_Blocker.html): */
46
47dcblocker(x)	= (x-x') : (+ ~ *(0.995));
48
49// resonant lowpass
50
51// This is a tweaked Butterworth filter by David Werner and Patrice Tarrabia,
52// see http://www.musicdsp.org and http://www.experimentalscene.com for
53// details.
54
55// res = resonance in dB above DC gain
56// freq = cutoff frequency
57
58lowpass(res,freq)	= f : (+ ~ g) : *(a)
59with {
60	f(x)	= a0*x+a1*x'+a2*x'';
61	g(y)	= 0-b1*y-b2*y';
62	a	= 1/db2linear(0.5*res);
63
64	c	= 1.0/tan(PI*(freq/SR));
65	c2	= c*c;
66	r	= 1/db2linear(2.0*res);
67	q	= sqrt(2.0)*r;
68	a0	= 1.0/(1.0+(q*c)+(c2));
69	a1	= 2.0*a0;
70	a2	= a0;
71	b1	= 2.0*a0*(1.0-c2);
72	b2	= a0*(1.0-q*c+c2);
73};
74
75/* Fuzz effect. */
76
77clip(x)		= f*x+1-f with { f = abs(drive*x)<=1; };
78fuzz(freq)	= clip : lowpass(res,tone*freq) : *(level);
79
80/* Karplus-Strong string synthesizer: */
81
82process	= vgroup("1-excitator", noise*gain : *(gate : excitator))
83	: vgroup("2-resonator", resonator(SR/freq)) : dcblocker
84        : vgroup("3-fuzz", fuzz(freq))
85        : vgroup("4-master", *(vol) : panner(pan));
86