diff -urN midi_prog-/Makefile midi_prog/Makefile
--- midi_prog-/Makefile	2015-04-21 00:00:00.000000000 +0900
+++ midi_prog/Makefile	2015-04-29 00:00:00.000000000 +0900
@@ -7,8 +7,9 @@
 CFLAGS += -Wall -I..
 
 VCD_OBJS = vcd.o in.o filter.o out.o wrt.o util.o
+VOCO_OBJS = voco.o vco.o wave.o in.o filter.o out.o util.o
 
-all: $(TARG) vcd
+all: $(TARG) vcd voco
 
 $(TARG): $(OBJS)
 	$(CC) -o $@ $(OBJS) $(LIB)
@@ -16,8 +17,11 @@
 vcd: $(VCD_OBJS)
 	$(CC) -o $@ $(VCD_OBJS) -lm
 
+voco: $(VOCO_OBJS)
+	$(CC) -o $@ $(VOCO_OBJS) -lm
+
 clean:
 	rm -f $(TARG) $(OBJS) *~
-	rm -f vcd $(VCD_OBJS)
+	rm -f vcd $(VCD_OBJS) voco $(VOCO_OBJS)
 
 # EOF
diff -urN midi_prog-/in.c midi_prog/in.c
--- midi_prog-/in.c	2015-04-20 00:00:00.000000000 +0900
+++ midi_prog/in.c	2015-04-29 00:00:00.000000000 +0900
@@ -11,3 +11,11 @@
 	*vp = (double)(c - inp->base) / inp->amp;
 	return 0;
 }
+
+int
+in_do2(in_rec_t *inp, double *vp)
+{
+	int i;
+	for(i=0; i<inp->ch_num; i++) if(in_do(inp, &vp[i]) == EOF) return EOF;
+	return 0;
+}
diff -urN midi_prog-/in.h midi_prog/in.h
--- midi_prog-/in.h	2015-04-20 00:00:00.000000000 +0900
+++ midi_prog/in.h	2015-04-29 00:00:00.000000000 +0900
@@ -6,5 +6,6 @@
 typedef struct out_rec in_rec_t;
 
 int in_do(in_rec_t *inp, double *vp);
+int in_do2(in_rec_t *inp, double *vp);
 
 #endif
diff -urN midi_prog-/out.c midi_prog/out.c
--- midi_prog-/out.c	2014-04-05 22:00:00.000000000 +0900
+++ midi_prog/out.c	2015-04-29 00:00:00.000000000 +0900
@@ -77,5 +77,11 @@
 	}
 }
 
-/* EOF */
+void
+out_do2(struct out_rec *ot, double *vp)
+{
+	int i;
+	for(i=0; i<ot->ch_num; i++) out_do(ot, vp[i]);
+}
 
+/* EOF */
diff -urN midi_prog-/out.h midi_prog/out.h
--- midi_prog-/out.h	2014-01-25 00:00:00.000000000 +0900
+++ midi_prog/out.h	2015-04-29 00:00:00.000000000 +0900
@@ -19,5 +19,6 @@
 
 void out_init(struct out_rec *ot, int ac, char **av);
 void out_do(struct out_rec *ot, double v);
+void out_do2(struct out_rec *ot, double *vp);
 
 #endif
diff -urN midi_prog-/voco.c midi_prog/voco.c
--- midi_prog-/voco.c	1970-01-01 09:00:00.000000000 +0900
+++ midi_prog/voco.c	2015-04-29 00:00:00.000000000 +0900
@@ -0,0 +1,164 @@
+#include "util.h"
+#include "vco.h"
+#include "in.h"
+#include "filter.h"
+#include "out.h"
+#include "ch.h"
+
+struct out_rec otr;
+in_rec_t in_carrier, in_voice;
+
+struct band_rec{
+	int fl, fh, n;
+} band;
+
+struct voco_rec{
+	struct filter_rec bpf, lpf;
+	struct filter_stat_rec stat_carrier, stat_voice, stat_lpf;
+	double v_c[2], v_v[2];
+} *voco_inf;
+
+FILE *
+fp_get(char *key, int ac, char **av, char *def_fn, char *mode)
+{
+	char *fn = opt_str(key, ac, av, def_fn);
+	if(fn == NULL) return NULL;
+	if(strcmp(fn, "-") == 0) return strcmp(mode, "r") == 0 ? stdin : stdout;
+	return fopen(fn, mode);
+}
+
+double *
+adj_vol_init(int ac, char **av)
+{
+	double *adj_vol, v;
+	char *s, s_idx[8], buf[1024];
+	int i;
+
+	if((adj_vol = malloc(sizeof(*adj_vol) * band.n)) == NULL) ERR("No Mem");
+	for(i=0; i<band.n; i++) adj_vol[i] = 1;
+	if((s = opt_str("-vol", ac, av, NULL)) != NULL){
+		while(*s && sscanf(s, "%[^:]:%s", s_idx, buf) == 2){
+			v = strtod(buf, &s);
+			if(strcmp(s_idx, "all") == 0){
+				for(i=0; i<band.n; i++) adj_vol[i] = v;
+			}else{
+				i = strtol(s_idx, NULL, 0);
+				if(0 <= i && i < band.n) adj_vol[i] = v;
+			}
+			if(*s == ',') s++;
+		}
+	}
+	return adj_vol;
+}
+
+double
+freq_get(int i)
+{
+	double l = log(band.fl), h = log(band.fh);
+	return exp(l + (h - l) * i / (band.n - 1));
+}
+
+void
+voco_init(struct voco_rec *voco, int ac, char **av, int i)
+{
+	voco->bpf.type = BPF;
+	voco->bpf.freq = freq_get(i);
+	voco->bpf.Q = opt_double("-Q", ac, av, 20);
+	filter_init(&voco->bpf, &voco->stat_carrier, otr.smp_t);
+	filter_init(&voco->bpf, &voco->stat_voice, otr.smp_t);
+
+	voco->lpf.type = LPF;
+	voco->lpf.freq = opt_double("-lpf_freq", ac, av, 20);
+	voco->lpf.Q = opt_double("-lpf_Q", ac, av, 0.7);
+	filter_init(&voco->lpf, &voco->stat_lpf, otr.smp_t);
+}
+
+void
+vco_init(struct vco_rec *vco, int ac, char **av)
+{
+	vco->wave1 = opt_int("-wave1", ac, av, vco->wave1);
+	vco->wave2 = opt_int("-wave2", ac, av, vco->wave2);
+	vco->tune = opt_int("-tune", ac, av, vco->tune);
+	vco->mix = opt_double("-mix", ac, av, vco->mix);
+	vco->ring = opt_int("-mix", ac, av, vco->ring);
+	vco->alias_noise1 = opt_int("-alias_noise1", ac, av, vco->alias_noise1);
+	vco->alias_noise2 = opt_int("-alias_noise1", ac, av, vco->alias_noise2);
+}
+
+double
+vco_val(struct vco_rec *vco, struct vco_stat_rec *stat, double freq, double sec)
+{
+	double v1 = vco_out(vco->wave1, vco->alias_noise1, &stat[0], freq, sec, 0);
+	double v2 = vco_out(vco->wave2, vco->alias_noise2, &stat[1], freq, sec, vco->tune * (1.0 / 1200));
+	double v;
+	if(vco->ring){
+		v = v1 * v2;
+		v1 = (v1 + v2) * 0.5;
+		v2 = v;
+	}
+	return MIX(v1, v2, vco->mix);
+}
+
+int
+main(int ac, char **av)
+{
+	double v_c[2], v_v[2], v_o[2];
+	double *adj_vol;
+	int i, j;
+
+	struct vco_rec vco = { WAVE_SAW, WAVE_SAW, 10, 0.5, 0, 0, 0 };
+	double vco_f = opt_double("-vco_f", ac, av, 100);
+	struct vco_stat_rec stat_vco[2] = { { 0, vco_f, 0 }, { 0, vco_f, 0 } };
+
+	sscanf(opt_str("-band", ac, av, "500,3000/16"), "%d,%d/%d", &band.fl, &band.fh, &band.n);
+
+	out_init(&otr, ac, av);
+	otr.fp = fp_get("-o", ac, av, "-", "w");
+	in_carrier = in_voice = otr;
+	if((in_carrier.fp = fp_get("-carrier", ac, av, NULL, "r")) == NULL){
+		vco_init(&vco, ac, av);
+	}
+	in_voice.fp = fp_get("-voice", ac, av, NULL, "r");
+
+	if((voco_inf = malloc(sizeof(*voco_inf) * band.n)) == NULL) ERR("No Mem");
+	for(i=0; i<band.n; i++) voco_init(&voco_inf[i], ac, av, i);
+
+	adj_vol = adj_vol_init(ac, av);
+
+	for(;;){
+		if(in_carrier.fp){
+			if(in_do2(&in_carrier, v_c) == EOF) break;
+		}else{
+			v_c[0] = vco_val(&vco, stat_vco, vco_f, otr.sec);
+			for(j=1; j<in_carrier.ch_num; j++) v_c[j] = v_c[0];
+		}
+		for(i=0; i<band.n; i++){
+			for(j=0; j<in_carrier.ch_num; j++){
+				voco_inf[i].v_c[j] = filter_out(&voco_inf[i].stat_carrier, v_c[j]);
+			}
+		}
+
+		if(in_voice.fp){
+			if(in_do2(&in_voice, v_v) == EOF) break;
+			for(i=0; i<band.n; i++){
+				for(j=0; j<in_voice.ch_num; j++){
+					double v = filter_out(&voco_inf[i].stat_voice, v_v[j]);
+					voco_inf[i].v_v[j] = filter_out(&voco_inf[i].stat_lpf, v < 0 ? -v : v);
+				}
+			}
+		}
+
+		for(j=0; j<otr.ch_num; j++) v_o[j] = 0;
+		for(i=0; i<band.n; i++){
+			for(j=0; j<otr.ch_num; j++){
+				v_o[j] += voco_inf[i].v_c[j] * voco_inf[i].v_v[j] * adj_vol[i];
+			}
+		}	
+		for(j=0; j<otr.ch_num; j++) v_o[j] /= band.n;
+
+		otr.sec = otr.smp_t * otr.smp_cnt;
+		out_do2(&otr, v_o);
+		otr.smp_cnt++;
+	}
+	return 0;
+}