diff -urN midi_prog-/pitdet.c midi_prog/pitdet.c
--- midi_prog-/pitdet.c	2015-08-14 00:00:00.000000000 +0900
+++ midi_prog/pitdet.c	2015-08-22 00:00:00.000000000 +0900
@@ -1,32 +1,33 @@
 #include "pitdet.h"
 
 double
-pitdet_note_to_freq(double note)
+pitdet_note_to_freq(struct pitdet *pd, double note)
 {
-	return 440 * pow(2, (note - 69) / 12);
+	return 440 * pow(2, (note - 69 + pd->adj_cent * 0.01) / 12);
 }
 
 double
-pitdet_freq_to_note(double freq)
+pitdet_freq_to_note(struct pitdet *pd, double freq)
 {
-	return log(freq / 440) / log(2) * 12 + 69;
+	return log(freq / 440) / log(2) * 12 + 69 - pd->adj_cent * 0.01;
 }
 
 void
-pitdet_init(struct pitdet *pd, double smp_freq,
+pitdet_init(struct pitdet *pd, double smp_freq, int adj_cent,
 	    int div, double abuf_wsec)
 {
 	int j;
 
 	pd->div = div;
+	pd->adj_cent = adj_cent;
 	pd->m = pd->div * 128;
 	if((pd->arr = malloc(sizeof(*pd->arr) * pd->m)) == NULL) ERR("No Mem");
 
 	for(j=0; j<pd->m; j++){
-		double note = (double)j / pd->div - 0.5;
-		double next_note = (double)(j+1) / pd->div - 0.5;
-		double freq = pitdet_note_to_freq(note);
-		double next_freq = pitdet_note_to_freq(next_note);
+		double note = (j + 0.5) / pd->div - 0.5;
+		double next_note = (j + 1 + 0.5) / pd->div - 0.5;
+		double freq = pitdet_note_to_freq(pd, note);
+		double next_freq = pitdet_note_to_freq(pd, next_note);
 		int wn = (int) pitch_wn(freq, next_freq);
 
 		pitch_init(&pd->arr[j], smp_freq, freq, wn, abuf_wsec);
diff -urN midi_prog-/pitdet.h midi_prog/pitdet.h
--- midi_prog-/pitdet.h	2015-08-14 00:00:00.000000000 +0900
+++ midi_prog/pitdet.h	2015-08-22 00:00:00.000000000 +0900
@@ -5,6 +5,7 @@
 
 struct pitdet{
 	int div;
+	int adj_cent;
 	int m;
 	struct pitch *arr;
 
@@ -16,10 +17,10 @@
 	double max_v;
 };
 
-double pitdet_note_to_freq(double note);
-double pitdet_freq_to_note(double freq);
+double pitdet_note_to_freq(struct pitdet *pd, double note);
+double pitdet_freq_to_note(struct pitdet *pd, double freq);
 
-void pitdet_init(struct pitdet *pd, double smp_freq,
+void pitdet_init(struct pitdet *pd, double smp_freq, int adj_cent,
 		 int div, double abuf_wsec);
 
 void pitdet_add(struct pitdet *pd, double v);
diff -urN midi_prog-/tool.c midi_prog/tool.c
--- midi_prog-/tool.c	2015-08-14 00:00:00.000000000 +0900
+++ midi_prog/tool.c	2015-08-22 00:00:00.000000000 +0900
@@ -55,6 +55,51 @@
 	int j, js, je;
 	char s[32];
 	double sec = pd->oldest.sec;
+	int test_off = opt_idx("-test_off", ac, av) > 0;
+	struct{
+		int stat;
+		double v;
+	} *wk;
+
+	if((wk = malloc(sizeof(*wk) * pd->m)) == NULL) ERR("No Mem");
+
+	for(j=0; j<pd->m; j++){
+		struct pitch *p = &pd->arr[j];
+		wk[j].stat = 0;
+		wk[j].v = tbuf_get_dbl(&p->ab.tb, sec);
+	}
+
+	while(!test_off){
+		int t = -1, j;
+		double v_max = 0;
+		for(j=0; j<pd->m; j++){
+			if(wk[j].stat != 0) continue;
+			if(t < 0 || wk[j].v > v_max){
+				t = j;
+				v_max = wk[j].v;
+			}
+		}
+		if(t < 0) break;
+		wk[t].stat++;
+		
+		for(j=0; j<pd->m; j++){
+			double a, x, k;
+
+			if(wk[j].stat != 0) continue;
+
+			/*			
+			wn/(2*freq) = (wn+a)/(2*freq[j])
+			a = wn*freq[j]/freq - wn
+			  = wn*(freq[j]/freq - 1)
+			*/
+			a = pd->arr[t].wn * (pd->arr[j].freq / pd->arr[t].freq - 1);
+			x = a * M_PI;
+			k = sin(x) / x;
+			k = k < 0 ? -k : k;
+
+			wk[j].v -= wk[t].v * k;
+		}
+	}
 
 	sprintf(s, "sec=%f ", sec);
 	printf("%s", s);
@@ -62,8 +107,7 @@
 	show_spectre_modify_area(pd, ac, av, s, &js, &je);
 
 	for(j=js; j<je; j++){
-		struct pitch *p = &pd->arr[j];
-		double v = tbuf_get_dbl(&p->ab.tb, sec);
+		double v = wk[j].v;
 		int iv = (int)(10 * v / pd->max_v);
 
 		if(iv < 0) iv = -1;
@@ -73,6 +117,8 @@
 		if(pd->div > 1 && j % pd->div == pd->div-1 && j != je-1) putchar(' ');
 	}
 	putchar('\n');
+
+	free(wk);
 }
 
 int
@@ -82,11 +128,12 @@
 	double v;
 
 	struct pitdet pd;
+	int adj_cent = opt_int("-adj_cent", ac, av, 0);
 	int div = opt_int("-div", ac, av, 1);
 	double abuf_wsec = opt_double("-abuf_wsec", ac, av, 2.5);
 
 	in_init(&in, ac, av);
-	pitdet_init(&pd, in.smp_freq, div, abuf_wsec);
+	pitdet_init(&pd, in.smp_freq, adj_cent, div, abuf_wsec);
 
 	while(in_do_mono(&in, &v) != EOF){
 		pitdet_add(&pd, v);