diff -urN midi_prog-/pitdet.c midi_prog/pitdet.c
--- midi_prog-/pitdet.c	Tue Aug 25 00:00:00 2015
+++ midi_prog/pitdet.c	Wed Aug 26 01:00:00 2015
@@ -78,8 +78,14 @@
 			wn/(2*freq) = (wn+a)/(2*freq[j])
 			a = wn*freq[j]/freq - wn
 			  = wn*(freq[j]/freq - 1)
+
+			fix.
+
+			(wn[j]+a)/(2*freq) = wn[j]/(2*freq[j])
+			a = wn[j]*freq/freq[j] - wn[j]
+                          = wn[j]*(freq/freq[j] - 1)
 			*/
-			a = pd->arr[t].wn * (pd->arr[j].freq / pd->arr[t].freq - 1);
+			a = pd->arr[j].wn * (pd->arr[t].freq / pd->arr[j].freq - 1);
 			x = a * M_PI;
 			k = sin(x) / x;
 			k = ABS(k);