bytebeat.c

#include <math.h>
#include <stdio.h>

#define BITRATE 16000.0
#define TAU 6.2831853
#define R -127

double sqr(int i){
	return (i%2)?1.0/i:0;
}

double saw(int i){
	return 1.0/i;
}

double tri(int i){
	return (i%2)?( ((i/2)%2)?-1:1) * 1.0/(i*i) :0;
}

double envelope(double p, double a, double d, double s, double h, double r, double l){
	p = fmod(p,l);
	if (p <= a){
		return p/a;
	} else if (p <= d + a){
		return 1 - (1-s)/d*(p-a);
	} else if (p <= a + d + h){
		return s;
	} else if (p <= a + d + h + r){
		return s - (s/r)*(p - a - d - h);
	} else {
		return 0;
	}
}

double organ(int t, double note, double bound, double (*partial)(int)){
	if (note <= -64){
		return 0;
	}
	double input = t*TAU*440*pow(2,note/12.0)/BITRATE;

	double sum = 0;
	bound += 1;
	for (int i = 1; i <= (int)bound; ++i){
		sum += ((i==(int)bound)?fmod(bound,1):1) * (*partial)(i)*sin(i*input);
	}

	return sum;
}

double drum(int t, double b, double o, double n, double l){
	b = fmod(32*b,32*l) + o + 1;
	t = t/((int)b);
	if (b <= n*32){
		return sin(BITRATE*pow(t,4)) + sin(BITRATE*pow(t+1,4));
	} else {
		return 0;
	}
	
}

int melody[] = {5,R,5,5,8,5,R,R,8,R,10,15,12,R,R,R};
int bass[] = {5,3,5,3,5,R,8,R,5,3,5,3,5,-7,-7,R};
int main(){
	for (int t = 0;;++t){
		double beat = 1*t/BITRATE;
		int melody_note = melody[(int)(4*beat) % 16];
		int bass_note = bass[(int)(4*beat)%16];

		int offset = (((int)(beat/8) % 3)==2?3.5:4)*((int)(beat/8) % 3);
		double sample_l = (((sin(8*TAU*beat)+4)/8)*envelope(beat, 0.005, 1.0/8, 0, 0, 0, 1.0/4) * (
			                organ(t, melody_note - offset, 40, saw) * 0.1 +
			                organ(t, melody_note - 12 - offset + 24*(((int)beat/2)%2), 10, sqr) * 0.1
			            )*((((int)beat/2)%2)?1:0.3)*2 + 

		                envelope(beat, 0.01, 0, 1, 1/12.0 - 0.02, 0.01, 1/8.0) * (
		                	organ(t+20, -24 + bass_note - offset, 40, saw)*0.02 +
		                	organ(t, -36 + bass_note - offset, 100, saw)*0.05
		                ) +

		                envelope(beat, 0.01, 0, 1, 1/8.0 - 0.1, 0.1, 1/4.0) * (
		                	organ(t, 7+((int)(4*beat + 1)%2) - 12 - offset,40, saw)*0.04 +
		                	organ(t+80, 3+2*((int)(4*beat + 1)%2) - 12 - offset,40, tri)*0.04
		                ) +

		                organ(t, 5 - 24 - offset, 20, saw)*0.02 +
		                organ(t, 8 - 24 - offset, 20, saw)*0.01 +
		                organ(t, 12 - 24 - offset, 20, saw)*0.01 +

		                drum(t, beat, 1+9*((int)(2*beat + 1) % 2) ,((int)(2*beat) % 2)?0.2:0.42, 0.5)*0.05) * 0.5;

		double sample_r = (((sin(8*TAU*beat)+4)/8)*envelope(beat, 0.005, 1.0/8, 0, 0, 0, 1.0/4) * (
			                organ(t, melody_note - offset, 40, saw) * 0.1 +
			                organ(t, melody_note - 12 - offset + 24*(((int)beat/2)%2), 10, sqr) * 0.1
			            )*((((int)beat/2)%2)?0.3:1)*2 + 

		                envelope(beat, 0.01, 0, 1, 1/12.0 - 0.02, 0.01, 1/8.0) * (
		                	organ(t, -24 + bass_note - offset, 40, saw)*0.02 +
		                	organ(t+20, -36 + bass_note - offset, 40, saw)*0.05
		                ) +

		                envelope(beat, 0.01, 0, 1, 1/8.0 - 0.1, 0.1, 1/4.0) * (
		                	organ(t+80, 7+((int)(4*beat + 1)%2) - 12 - offset,40, saw)*0.04 +
		                	organ(t, 3+2*((int)(4*beat + 1)%2) - 12 - offset,40, tri)*0.04
		                ) +

		                organ(t, 5 - 24 - offset, 20, saw)*0.02 +
		                organ(t, 8 - 24 - offset, 20, saw)*0.02 +
		                organ(1.01*t, 12 - 24 - offset, 20, saw)*0.01 +

		                drum(t+100, beat, 1+9*((int)(2*beat + 1) % 2) ,((int)(2*beat) % 2)?0.2:0.42, 0.5)*0.05) * 0.5
		                ;
		int output_l = sample_l * 65535;
		int output_r = sample_r * 65535;
    	putchar(output_l >> 8);
    	putchar(output_l);
    	putchar(output_r >> 8);
    	putchar(output_r);
	}
}