diff --git a/include/sound4calc.h b/include/sound4calc.h
index 5e6e000..2531984 100644
--- a/include/sound4calc.h
+++ b/include/sound4calc.h
@@ -3,11 +3,17 @@
 
 extern struct Note
 {
-    char* wave_signal;
+    struct Wave wave;
     unsigned short duration;
     unsigned int freq;
 } note;
 
+struct Wave
+{
+    char* signal;
+    unsigned short length;
+};
+
 void CallSequence();
 void CallNote();
 void PutPinState(char level);
diff --git a/src/main.c b/src/main.c
index 1ffb0e0..d0ed060 100644
--- a/src/main.c
+++ b/src/main.c
@@ -19,11 +19,13 @@ int main(void)
         dclear();
 
         dprint(1, 1, "%d", note.freq);
-        dprint(1, 10, "%s", note.wave_signal);
-        dprint(1, 20, "%d, %d", strlen(note.wave_signal), place);
+        dprint(1, 10, "%s", note.wave.signal);
+        dprint(1, 20, "%d", place);
         dprint(1, 30, "F1:note/F2:sequence");
         dtext(1, 50, "F5 _    F6 -");
 
+        note.wave.length = place;
+
         dupdate();
 
         key = getkey();
@@ -35,9 +37,9 @@ int main(void)
             case KEY_UP : note.freq+=10; break;
             case KEY_DOWN : note.freq-=10; break;
 
-            case KEY_F5 : *(note.wave_signal+place++) = '_'; break;
-            case KEY_F6 : *(note.wave_signal+place++) = '-'; break;
-            case KEY_DEL : place=(place>0 ? place - 1 : 0); *(note.wave_signal+place) = 0; break;
+            case KEY_F5 : *(note.wave.signal+place++) = '_'; break;
+            case KEY_F6 : *(note.wave.signal+place++) = '-'; break;
+            case KEY_DEL : place=(place>0 ? place - 1 : 0); *(note.wave.signal+place) = 0; break;
 
             case KEY_F1 : CallNote(); break;
             case KEY_F2 : CallSequence(); break;
diff --git a/src/sound4calc.c b/src/sound4calc.c
index 741618b..d575d9a 100644
--- a/src/sound4calc.c
+++ b/src/sound4calc.c
@@ -38,7 +38,7 @@ void CallSequence()
         }
 
         // update of the number of turn
-        length_end = strlen(note.wave_signal) * seq[notes].freq * seq[notes].length_ms / 1000;
+        length_end = strlen(note.wave.signal) * seq[notes].freq * seq[notes].length_ms / 1000;
         // start or reload the timer
         timer_start(TIMER_USER, 2 * seq[notes].freq, Clock_Hz, CallSequence, 0);
     }
@@ -50,7 +50,7 @@ void CallSequence()
 void CallNote()
 {
     note.duration = 1000;
-    timer_start(TIMER_USER, note.freq * strlen(note.wave_signal), Clock_Hz, PlayNote, strlen(note.wave_signal) * note.freq * note.duration / 1000);
+    timer_start(TIMER_USER, note.freq * note.wave.length, Clock_Hz, PlayNote, note.wave.length * note.freq * note.duration / 1000);
 }
 
 /*
@@ -68,9 +68,9 @@ void PlayNote()
 {
     static int x = 0;
 
-    PutPinState(note.wave_signal[x]=='-');
+    PutPinState(note.wave.signal[x]=='-');
     x = x + 1;
-    if(!(note.wave_signal[x])) x = 0;
+    if(!(note.wave.signal[x])) x = 0;
 }
 
 /*